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UNIVERSITY  OF  ILLINOIS, 

Agricultural  Experiment  Station. 

URBANA,  MAY,  1896. 


BULLETIN  NO.  44. 


INSECT  INJURIES  TO  THE  SEED  AND  ROOT  OF 
INDIAN  CORN  * 


INTRODUCTORY. 


The  corn  insects  now  recognized  as  in  some  way  and  to  some 
extent  injurious  to  some  part  of  the  plant  number  214  species, 
of  which  1 8  are  known  to  infest  the  seed,  27  the  root  and  the  sub- 
terranean part  of  the  stalk,  76  the  stalk  above  ground,  118  the 
leaf,  19  the  blossom, — that  is  the  tassel  and  the  silk, — 42  the  ear  in  the 
field,  2  the  stacked  fodder,  and  24  the  corn  in  store,  either  whole 
or  ground.  The  greater  part  of  this  long  list,  which  is  doubtless 
by  no  means  really  complete,  is  composed  of  those  whose  injuries 
are  now  so  slight  or  rare  as  to  constitute  a  possible  menace  rather 
than  to  cause  a  serious  loss ;  but  the  history  of  economic  ento- 
mology, and  even  of  the  entomology  of  this  one  plant,  teaches  us 
that  we  can  rarely  tell  in  advance  what  to  expect  of  any  possibly 
injurious  species.  In  fact,  some  of  the  insect  enemies  of  corn  now 
most  destructive  were  not  many  years  ago  almost  unknown  even  to 
the  entomologist — the  northern  corn  root  worm  and  the  corn  root 
aphis,  for  example. 

The  principal  insect  species  infesting  this  plant  are  the  seed- 
corn  maggot  and  the  wireworms,  attacking  the  seed  ;  these  latter 

*This  article  is  an  abstract,  with  occasional  minor  alterations,  of  the  more  strictly 
economic  parts  of  the  Seventh  Report  of  the  writer  as  State  Entomologist  of  Illinois, 
first  published  in  February,  1895. 

209 


210  BULLETIN  NO.  44. 

insects,  the  white  grubs,  the  corn  root  worms,  and  the  root  aphis, 
affecting  the  roots ;  the  cutworms  and  root  web-worms,  the  army 
worm,  the  stalk-borer,  the  corn  worm,  the  bill-bugs,  the  chinch 
bug,  the  corn  flea-beetle,  and  the  grasshoppers,  injuring  stalk  and 
leaf;  the  corn  worm,  the  corn  root  worms,  and  the  grasshoppers, 
eating  the  flower  structures  and  the  ear ;  and  the  meal-moth  and  the 
weevils  devouring  the  kernel  in  the  granary  or  the  meal  in  the  bin. 
Of  these,  by  far  the  worst  at  present  are  the  wireworms,  the  corn 
root  worms,  the  white  grubs,  the  root  lice,  the  cutworms,  the 
chinch  bug,  the  grasshoppers,  and  the  army  worm. 

The  most  serious  ordinary  injuries  to  corn,  those  which  the 
plant  is  least  able  to  sustain,  are  injurious  to  the  seed  and  root, 
particularly  those  occurring  early  in  the  year ;  but  they  are,  for- 
tunately, those  against  which  precautionary  or  preventive  meas- 
ures may  be  most  readily  taken,  and  with  the  best  effect. 

'      GENERAL   INDICATIONS   OF   INJURY. 

Before  beginning  a  description  of  injuries  to  each  part  of  the 
plant,  a  few  practical  hints  may  be  given  which  will  aid  to  a  recog- 
nition of  insect  attack  from  the  general  aspect  of  the  field  or  from 
the  appearance  of  the  entire  plant. 

1.  If  corn  largely  fails  to  appear  in  due  time  after  planting, 
the  farmer  need  not  content  himself  with  a  surmise  that  his  seed 
was  poor  or  that  the  weather  has  been  unfavorable,  but  should 
examine  the  seed  itself  for  evidence  of  the  work  of  one  of  several 
insects  (wireworms,  seed-corn  maggots,  grass  maggots,  etc.}  attacking 
it  in  the  earth. 

2.  If  the  young  plants  make  an  unequal  start,  some  hills  ap- 
pearing earlier  and  growing  more  thriftily  than  others  at  the  very 
first,  the  roots  should  be  searched  for  the  corn  root  louse;  and  even 
those  hills  should  be  examined  in  which  the  corn  has  not  yet  come 
up,  as  this  louse  sometimes  infests  the  sprouting  plant  before  it 
appears  above  ground. 

3.  The  ab'undant  occurrence  of  ants  in  the  corn  field,  sinking 
their  burrows  among  the  stalks   of   the  hill,  is  evidence  of  the 
presence  of  the  corn  root  louse  in  their  company. 

4.  If  the  growth  of  the  corn  is  arrested  or  retarded  in  patches 
throughout  the  field,  the  leaves  turning  first  yellow  and  then  red, 
it  is  likely  that  the  roots  are  infested  by  the  same  root  louse,  to  be 
discovered  by  carefully  digging  up  the  hill  and  picking  or  gently 
shaking  off  the  earth  to  expose  the  roots  at  their  origin.     If  no 
insect  enemy  is  found,  the  difficulty  is  quite  likely  to  be  due  to  a 
fungus  attack  known  as  the  root  blight  of  corn,  a  discussion   of 
which  does  not  come  within  the  scope  of  this  article.   [See  page  234.] 


l8g6.J        INSECT  INJURIES  TO  SEED  AND  ROOT  OF  CORN.  211 

5.  If  single  stalks  or  entire  hills  are  killed  or  withered  when 
a  foot  high  or  less,  search  should  be  made  among  the  roots  and  on 
the  stalk  below  the  surface  for  the  wireworms  and  the  white  grubs 

6.  If  the  corn  falls  readily  in  a  windy  storm  and  does  not 
afterward  rise,  and  if  it  may  be  pulled  up  easily  after  the  ear  has 
begun  to  form,  it  is  probable  that  the  roots  are  infested  by  the  corn 
root  worms  or  that  they  have  been  eaten  by  white  grubs. 

7.  If  the  plant  remains  green  too  long,  maturing  slowly,  and 
if  the  field  contains  many  sterile  stalks  or  soft,  imperfect  nubbins, 
it  is  likely  that  the  common  corn  root  worm,  in  some  of  its  stages, 
will  be  found  in  or  among  the  roots  if  search  be  made  before  Sep- 
tember I.     If  large  numbers  of  grass-green  beetles  one-fifth  of  an 
inch  in  length  (about  the  size  of  a  common  red  ladybug)  are  seeft 
on  the  silks  and  tassels  of  the  corn,   or  feeding  upon  the  fallen 
pollen  collected  at  the  bases  of  the  leaves,  or  upon  the  blossoms  of 
ragweed  or  other  flowering  plants  in  the  field,  the  crop  has  suffered 
from  an  attack  of  the  corn  root  worm,  of  which  these  beetles  are 
the  adult,  and  the  ground  should  be  planted  to  some  other  crop 
the  following  year. 

8.  A  deformed  and  unequal  growth  of  the  foliage,  especially 
of  that  unfolding  from  the  roll  of  leaves  at  the  growing  tip  of  the 
plant,  with  more  or  less  irregular  and  ragged  injury,  when  the  corn 
is  from  one  to  two  feet  high,  is  often  due  to  an  attack  by  the  first 
generation  of  the  corn  worm,  the  second  generation  of  which  bur- 
rows in  the  kernels  of  the  ear  of  corn  during  late  summer  and 
early  fall. 

9.  On  the  other  hand,  the  presence  of  elongate  holes,  placed 
side  by  side  in  an  orderly  manner,  in  short  rows  extending  across 
the  well-opened  leaf,  is  commonly  the  mark  of  an  injury  done  when 
the  corn  was  smaller  by  the  corn  bill-bugs,  several  species  of  which 
will  be  described  when  injuries  to  the  leaf  are  under  discussion. 

10.  An  irregular  eating  away  of  the  leaves  of  young  corn, 
and  a  similarly  irregular  gnawing  of  the   stalk  near  the  ground 
when  the  plant  is  less  than  a  foot  in  height,  should  lead  to  an 
examination  of  the  earth  about  the  base  of  the  hill.     If  fine  particles 
and  small  lumps  of  earth  are  found  more  or  less  closely  webbed 
together  in  a  mass  approximating  the  size  of  a  hickory  nut,  some 
one  or  more  of  the  species  of  root  web-worms  are  doubtless  at  work 
in  the  field. 

11.  The  cutting  of  the  young  corn  at  or  below  the  surface  of 
the  ground  is  an  injury  too  well  known  as  the  work  of  the  cut- 
worms to  require  more  than  bare  mention  here. 

12.  The  appearance  in  the  side  of  the  stalk  of  a  hole  about  the 
size  of  a  straw,  with  a  brown  moist  powder  exuding,  is  evidence  of 


212  BULLETIN   NO.   44.  [May, 

the  presence  of  the  stalk-borer,  an  insect  which  often  does  a  great 
and  practically  irremediable  damage  to  young  corn  in  early  spring, 
especially  in  low  grounds,  by  burrowing  the  stalk,  pushing  more 
or  less  of  its  excrement  out  at  the  mouth  of  its  burrow. 

13.  A  similar,  equally  evident  burrowing  of  the  ear,  the  ex- 
crement from  which  escapes  by  a  hole  through  the  green  husks  or 
becomes  mixed  through  the  silks  at  the  tip  of  the  ear,  betrays  the 
presence  of  the  corn  worm  already  mentioned  under  8. 

14.  The  eating  away  of  the  blade  of  the  leaf  in  late  summer 
and  autumn  so  as  to  make  large  irregular  holes,  which  may  multiply 
and  increase  in  size  until  they  finally  leave  only  the  stripped  midrib 
and  the  bare  stalk — the  injury  being  commonly  very  much  worse 
^ilong  the  edges  of  the  field — is  commonly  due  to  grasshoppers. 

15.  In  the  corn  crib  or  granary  the  commonest  serious  mis- 
chief is  the  peppering  of  the  kernel  with  little  round  holes,  each 
the  diameter  of  the  head  of  a  pin,  the  first  suspicion  of  which  will 
frequently  be  aroused  by  the  appearance  of  fine  particles  of  meal 
sifting  down  somewhere  within  sight.     The  insect  most  likely  to 
be  responsible  for  this  mischief  is  the  corn  -moth;  but  various  weevil 
species  may  also  be  involved. 

SYNOPSIS   OF  INJURIES. 

A.      INJURIES   TO   THE   SEED   IN   THE   EARTH. 

1.  Injuries  by  ants,  which  hollow  out  the  kernel,  commonly  scat- 

tering the  meal  through  the  dirt.     Page  214  (Fig.  i  and  2.) 

2.  Injuries  by  small  beetles,  which  gnaw  the  kernel  from  without, 

commonly  beginning  at  the  germ.     Pages  215-217  (Fig.  3, 
4,  and  5.) 

3.  Injuries  by  footless  maggots,  which  bury  themselves  in  the 

seed.     Page  218. 

Seed-corn  Maggot.     Page  218  (Fig.  6,  7,  8,  and  9.) 
Black-headed  Grass  Maggot.     Page  220  (Fig.  10.) 

4.  Injuries  by  six-legged  larvae,  which  gnaw  or  bore  through  the 

kernel.     Page  220. 

Pale-striped  Flea-beetle.     Page  221  (Fig.  n,  12  and  13.) 
The  Banded  Ips.     Page  222  (Fig.  14,  15,  and  16.) 
Wireworms.     Pages  224-233  (Fig.  17-32.) 

B.      INJURIES   TO   THE   ROOTS. 

5.  Roots  deadened,  hardened,  or  dwarfed,  without  apparent  loss 

of  substance.     Page  235, 


l8g6.J        INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  213 

a.  Small  brown  or  yellowish  ants  abundant  in  the  hills,  and 

bluish  green  or  whitish  root  lice  (plant  lice  and  mealy 
bugs)  on  the  larger  roots.  Page  235. 

The  Corn  Root  Aphis.     Page  237  (Fig.  33-37.) 

The  Grass  Root  Louse.     Pages  256,  257  (Fig.  40  and  41.) 

b.  No  notable  number  of  insects  present.     The   lowest  roots 

dead;  surface  of  underground  part  of  stalk  with  brown- 
ish corroded  spots,  interior  of  this  part  darker,  at  least 
at  the  joints,  while  the  spaces  between  may  be  seem- 
ingly healthy.  (Root  blight  of  corn,  a  bacterial  disease; 
not  entomological.)  Page  234. 

6.     Roots  evidently  injured  or  destroyed  by  perforations,  gnawing, 
burrowing,  decay  or  other  loss  of  substance.     Page  257. 

a.  Roots  eaten  away,  not  burrowed  or  perforated,  and  without 

rotten  or  withered  tips;  tap-root  commonly  gone  or 
decayed.  White  grubs  in  soil  among  or  beneath  the 
roots.  Page  257. 

White  Grubs.     Pages  257-280  (Fig.  42-48.) 
Prionus  Grubs.     Page  281  (Fig.  49-51.) 

b.  Roots  penetrated,  perforated,  irregularly  burrowed,  and  more 

or  less  eaten  off  and  eaten  up.  Underground  parts  of 
stalk  also  similarly  injured.  Page  282. 

Wireworms  in  soil  among  the  roots.     Pages  224-233  (Fig. 

17-32.) 
Small,  slender,  soft-bodied,  yellowish  white  grubs  in  the 

roots  and  earth.      (The  Southern   Corn   Root  Worm.) 

Page  282  (Fig.  52-56.) 

c.  Roots   visibly  penetrated    and   perforated    scarcely   at   all; 

sometimes  decayed  at  tips,  but  not  eaten  away.  Princi- 
pal injury  interior,  in  form  of  minute  burrows  which 
are  commonly  longitudinal,  discoverable  on  peeling  or 
splitting  the  root,  the  burrows  sometimes  containing 
minute  slender  white  six-legged  larvae,  with  brown  head 
and  neck  and  brown  patch  on  last  segment.  (The 
Northern  Corn  Root  Worm.)  Page  287  (Fig.  57-61.) 


214  BULLETIN  NO.  44.  [May, 

A.  DETAILED  DISCUSSION  OF  INJURIES  TO  THE  SEED. 

i .  Injuries  by  ants,  which  hollow  out  the  kernel,  commonly  scat- 
tering the  meal  through  the  dirt. 

Injuries  to  corn  by  ants  are  of  two  kinds :  one  indirect  but 
serious;  the  other  direct,  but  of  little  importance  because  quite 
rare.  The  former  will  be  treated  in  connection  with  insects  affect- 
ing the  root,  since  it  is  by  rearing,  transporting,  and  fostering 
the  root  lice  of  corn  that  ants  are  most  injurious ;  and  the  latter 
is  given  here  in  its  place  as  an  injury  to  the  seed  in  the  earth. 

Occasionally  in  searching  for  the  causes  of  the  failure  of  corn 
to  germinate,  or  to  grow  thriftily  after  making  its  appearance,  a 
kernel  may  be  found  wholly  or  partly  hollowed  out,  the  mealy 
interior  being  not  devoured,  but  scattered  about  in  the  earth, 
while  the  outer  shell  of  the  seed  remains  but  little  disturbed.  The 
agents  of  this  small  mischief  will  frequently  be  found  still  buried 
in  the  cavities  they  have  excavated — most  commonly  ants  of  a 
minute  pale  yellow  species,  a  little  more  than  a  sixteenth  of  an 
inch  in  length.  This  injury  to  corn  requires  no  treatment  so  far 
as  is  now  known,  and  probably  admits  of  none.  I  have  seen  two 
species  of  ants  engaged  in  this  injury  to  planted  corn  in  Illinois : 
one  the  common  little  house  ant*,  which  frequently  becomes  a 
nuisance  in  pantries,  especially  if  sugar  is  exposed  to  its  visita- 
tions (see  Fig.  i);  and  the  other  a  larger,  outdoor  species,  well 
shown  in  Fig.  2. 

The  first  of  these  ants  (Fig.  i)  was 
found  by  me  abundant  in  many  fields  of 
corn,  both  new  and  old,  at  Normal,  Illinois, 
in  June,  1883,  and  at  Champaign  in  May, 

1886,  where   they    were   usually   collected 
about  the   kernels  in  the    earth,   and  fre- 
quently more  or  less  hidden  in  little  cavities 
excavated  in  the  softened  grain.     May  19, 

1887,  they  were  very  abundant  in  a  field  of 
corn  on  sod  in  Champaign  county,  eating 

¥iG.~\.-Solenopsis  molesta,0^  the  planted  kernels.      In    autumn   the 

worker;  enlarged  eighteen    same    species    has   been    detected    by    us 

diameters.  indulging  a  similar  appetite,  but  in  a  way 

to  do  no  harm.     September  11-21,  1893,  it  was  found  feeding  on 

and  within  kernels  of  corn  at  the  tips  of  ears  which  had  evidently 

been  injured  previously  by  crickets  and  grasshoppers.     The  solid 

substance  of  the  grain  is  not  actually  eaten  by  these  ants, — a  fact 

which  I  demonstrated  by  dissection  of  the  ants, — but  it  is  simply 

*Solenopsis  molesta,  Say   (=S.  debilis,  Mayr). 


1896.]         INSECT  INJURIES   TO   SEED  AND   ROOT  OF   CORN.  21$ 

gnawed  away,  doubtless  for  the  sake  of  the  sweetish  and  oily 
fluids  of  the  softened  kernels.  If  plants  start  from  seeds  thus 
injured,  they  are  shorter  than  those  adjacent,  and  have  a  stunted, 
weak  appearance. 

This  species  has  also  been  several  times  noticed  by  us  in  Sep- 
tember in  attendance  upon  the  root  louse  of  corn,  sharing  with 
several  other  species  of  ants  the  cares  and  benefits  of  this  associa- 
tion. It  occurs  more  frequently,  according  to  our  observations, 
at  this  season  of  the  year,  with  the  corn  root  lice  infesting  purs- 
lane than  with  those  upon  the  corn  itself.  I  have  also  recorded  in 
my  Thirteenth  Report  (p.  112)  observations  of  injuries  to  ripe 
strawberries  by  this  house  ant.  • 

The  second  species  referred  to 
in  this  connection  (Fig.  2)  was  seen 
by  us  in  Champaign,  May  13,  1887,  tear- 
ing off  fragments  from  a  kernel  of 
sprouted  corn  just  below  the  surface 
of  the  soil,  disposing  of  them  much  as 
does  the  species  mentioned  above. 
Many  other  grains  were  found  in  differ- 
ent parts  of  the  same  field  similarly 
injured,  being  sometimes,  indeed,  com- 
pletely excavated.  The  abundance 
of  this  species  and  the  obscurity  of 
the  injury  suggest  that  it  may  do 
greater  mischief  than  would  appear  FlG-  *-Myrmica  scabrinodis  lobi- 

"  .  corms,  worker ;  enlarged  eight 

from  this  Statement.  and  one-half  diameters. 

This  species,  like  the  preceding,  feeds  in  fall  upon  kernels  of 
corn  at  the  tip  of  the  ear  in  the  field,  most  frequently  following 
injuries  by  other  insects,  but  certainly  sometimes  hollowing  out 
the  grain  without  their  aid. 

Its  relations  to  the  corn  plant  louse  will  be  described  in  another 
article. 

2.  Injuries  by  small  beetles*  which  gnaw  away  the  kernel  from 
withoiit,  commonly  beginning  at  the  germ. 

Three  common  beetles  have  been  detected  by  us  and  reported 
by  others  as  engaged  in  a  somewhat  noticeable  injury  to  seed 
corn  in  the  earth,  two  of  them  among  the  most  abundant  of  our 

*  Beetles  commonly  have  four  wings,  the  front  pair  of  which  are  usually  hard,  thick, 
and  opaque,  fitting  more  or  less  closely  upon  the  hinder  part  of  the  body  above,  and 
similar  in  appearance  to  the  rest  of  the  upper  surface.  Beneath  these,  and  next  to  the 
body,  may  be  found  the  membranous  hind  wings,  generally  entirely  concealed  except 
during  flight.  The  segment  bearing  the  hind  legs  is  fixedly  attached  to  the  hind  body, 
but  by  a  movable  articulation.  They  also  have  a  biting  mouth  furnished  with  two  pairs 
of  jaws. 


2l6 


BULLETIN   NO.   44. 


[May, 


FlG.  3. — Agonoderus  pallipes,  imaigo  ;  en- 
larged four  and  one-fourth  diameters ; 
its  work  in  seed  corn. 


Illinois  insects,  and  the  third  also  common,  but  too  small  to  be 
noticed  frequently  by  the  ordinary  observer. 

The  first  of  these  is  an  oblong  pale  brown  beetle  (Agonoderus 
pallipes)  with  a  blackish  cloud  on  the  back,  from  a  half  to  a  third  of 

an  inch  in  length  and  about  a 
third  as  wide  as  long.  It  will  be 
easily  recognized  by  the  illustra- 
tion (Fig.  3).  It  is  a  species  of 
common  notoriety  (although  it 
has  never  received  an  English 
name)  because  of  its  annoying 
abundance  at  lights  in  early 
spring.  Hibernating  as  an  adult, 
it  leaves  its  winter  quarters  with 
the  first  warm  sunny  days,  and 
flies  abroad  at  night  in  countless 
myriads.  Shortly  afterwards  the  eggs  are  laid  in  the  earth,  and  a 
new  generation  comes  forth  abundantly  in  June  and  July.  The 
adults  themselves  may  be  found,  however,  throughout  the  year. 
It  is  possible  that  more  than  one  generation  occurs  in  a  season. 
We  have  noticed,  in  fact,  a  disagreeable  abundance  of  these 
beetles  at  lights  on  warm  September  evenings.  The  species 
ranges  throughout  all,  or  the  greater  part,  of  the  United  States  and 
Canada. 

It  was  first  made  known  to  me  as  injurious  to  seed  corn  in  the 
ground  by  a  note  from  Mr.  Thomas  Huber,  of  Illinois  City,  Rock 
Island  county,  dated  June  4,  1883,  and  accompanied  by  a  specimen 
of  the  beetle  "found  in  seed  corn,  buried  in  the  kernel,  eating  the 
germ  and  part  of  the  inside."  In  Bulletin  No.  12  of  the  U.  S. 
Department  of  Agriculture,  Division  of  Entomology  (p.  44)^ 
Professor  Riley  reports  the  receipt  of  this  beetle  during  the  sum- 
mer of  1885,  with  the  information  that  it  was  injuring  young  corn 
by  gnawing  into  the  seed  and  by  eating  the  sprouting  roots.  One 
of  these  observations  was  confirmed  by  the  sending  of  a  specimen 
together  with  an  injured  grain.  The  exact  amount  of  damage  was 
not  stated,  but  it  was  said  to  be  quite  extensive.  Even  before  these 
observations  I  had  myself  detected  this  beetle  injuring  the  roots 
of  corn  to  some  small  extent;*  a  point  determined  by  the  dissec- 
tion of  specimens  taken  in  corn  fields,  among  the  roots.  Nearly 
half  the  food  of  these  dissected  specimens,  however,  consisted  of 
fragments  of  chinch  bugs,  and  other  insect  remains.  The  character 
and  amount  of  this  injury  to  corn  have  not  heretofore  been  such  as 


"Twelfth  Rep.  State  Ent.  111.,  p.  43. 


1896. J        INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  2I/ 


imago  ;  enlarged  six  and 
one-half  diameters. 


to  call  for  protective  treatment,  but  if  the  beetle  should  become 
sufficiently  destructive  to  make  such  measures  profitable,  it  is  likely 
that  "a  satisfactory  remedy  will  be  found  in  soaking  all  seed  corn  for 
a  short  time  before  planting  in  some  arsenical  solution,  such  as 
Paris  green  or  London  purple,  in  water.  Such  a  course  will  not 
injure  the  germinative  quality  of  the  seed,  and  will  probably  result 
in  the  death  of  all  beetles  which  attempt  to  gnaw  the  seed."* 

'  The  fact  that  a  common  small  shin- 
ing black  dung  beetle,  Aphodius granarius 
(Fig.  4),  very  abundant  in  stable  manure, 
where  it  feeds  in  part  on  fragments  of  un- 
digested grain,  may  under  favoring  con- 
ditions transfer  its  attentions  to  seed 
corn  in  the  hill,  gives  occasion  for  brief 
mention  of  this  insect  here. 

Our  only  knowledge  of  this  injury 
comes  from  Professor  C.  H.  Fernald  of 

the  Massachusetts  Agricultural  College,t   FlG-  ^—Aphodius granarius, 
who  received  specimens  of  this   beetle 
from  Lancaster,  Massachusetts,  with  the 
statement  that  they  had  been  found  destroying  seed  corn  in  the 
ground  before  it  sprouted. 

The  third  of  these  small  beetles, 
Clivina  impressifrons  (Fig.  5),  is  included 
among  insects  injurious  to  seed  corn 
upon  the  evidence  of  a  single  observation 
made  by  Mr.  F.  M.  Webster  in  Indiana. 
He  says :  "  I  received  from  Whitly 
county,  Indiana,  a  considerable  number 
of  these  beetles,  with  the  statement  that 
they  were  found  in  a  piece  of  ground 
which  had  been  broken  the  preceding 
spring,  the  field  being  swampy  and  of  a 
black  soil,  like  those  infested  by  wire- 
worms.  The  beetles  attacked  the  seed 
grains  as  soon  as  the  latter  became 
moistened.  When  received,  one  of  the 
beetles  had  burrowed  into  a  kernel 
of  corn  in  the  vicinity  of  the  germ, 

..."  .  . ,  ,       FlG.  5 — Clivina  impressifrons, 

and  was  engaged  in  devouring  the  sub-        enlarged  eight  and  one- 

Stance."  half  diameters. 


*Bull.  No.  12,  U.  S.  Department  of  Agriculture,  Division  of  Entomology,  p.  45. 
tBull.  No.  i,  Hatch  Experiment  Station,  Mass.  Agr.  Coll.,  p.  3. 


2l8  BULLETIN  NO.   44.  \May, 

3.  Injuries  by  footless  maggots,  which  bury  themselves  in  the 
seed  grain. 

Two  rather  common  injuries  to  seed  corn  in  the  ground  are 
due  to  small  white  maggots  without  legs,  one  apparently  headless, 
with  much  the  form  and  general  appearance  of  a  very  small  blow- 
fly larva,  and  the  other  with  a  smooth,  conspicuous  head  of  a  shin- 
ing jet  black  color.  The  first  is  known  as  the  seed-corn  maggot, 
and  infests  corn  only,  as  at  present  understood;  and  the  second  is 
the  black-headed  grass  maggot,  normally  a  grass  insect,  as  its 
name  implies,  and  injurious  to  corn  only  when  this  follows  grass. 
Both  these  maggots  penetrate  the  kernel,  feeding  on  the  mealy 
inner  part,  and  leaving  the  outer  shell.  The  first  changes  in  the 
course  of  the  summer  to  a  small  two-winged  fly  of  the  general  form 
of  the  house-fly,  and  the  second  becomes  a  slender,  small  black 
gnat,  roughly  resembling  the  mosquito.  The  fly  of  the  seed-corn 
maggot  is  little  likely  to  be  noticed  in  its  winged  state,  but  the 
gnat  of  the  grass  maggot  is  frequently  seen  in  very  large  numbers 
on  and  near  the  ground  in  early  spring. 

THE  SEED-CORN  MAGGOT. 
(Pkorbiafuscipes,  Zett.) 


FIG.  6. — Seed-corn  Maggot ;  enlarged  eleven  diameters. 

This  maggot  penetrates  the  grain  commonly  after  it  sprouts 
but  before  it  appears  above  ground,  killing  the  germ  or  the  g^ow- 
ing  shoot  and  finally  hollowing  out  the  interior  so  as  to  leave  only 
the  harder,  outer  parts  of  the  kernel.  In  specimens  of  injured  seed 
received  by  us  from  Altamont,  Illinois,  the  larva  had  bored  a  round 
hole  in  the  grain  near  the  edge,  and  mined  in  a  circular  direction 
around  the  germ.  In  other  grains  it  had  entered  at  the  tip  of  the 
germ,  and  in  some  beside  the  sprout.  In  one  plant  containing  a 
full-grown  maggot  about  two-thirds  imbedded  in  the  kernel,  a  root 
about  three  inches  long  had  formed,  and  a 
yellowish  stalk  had  grown  two  inches  in 
height.  Still  other  grains  had  almost  the 
whole  interior  eaten  out.  Unsprouted  ker- 
nels, softened  by  lying  in  the  earth,  are  also 
FIG.  7. — Seed  corn  injured  by  frequently  penetrated  in  a  way  to  destroy 
Seed-corn  Maggot.  ^he  germ.  Commonly  these  injuries  are 
trivial  in  amount,  but  in  at  least  one  instance  mentioned  by  Dr. 


1896.]         INSECT   INJURIES  TO   SEED   AND   ROOT   OF   CORN.  2IQ 


Riley  in  his  First  Report  as  State  Entomologist  of  Missouri  (p.  154), 
the  crop  of  a  field  in  New  Jersey  was  practically  destroyed.  This 
insect  is  now  known  to  attack  not  only  sprouting  corn  in  the  earth, 
but  also  the  roots  of  cabbages,  radishes,  onions,  beans,  and  mustard, 
and  the  eggs  of  locusts  (grasshoppers). 

The  adult  is  a  small  two-winged  fly,  about  a 
fifth   of  an  inch  in  length   of  body,  not  unlike  a 
house-fly  in  general  appearance,  but  smaller,  and 
of  a  lighter  form.     It  is  widely  distributed,  having 
been  reported  from  Europe, — where  it  seems  to 
have   originated, — and    also    from    Canada,    New 
Jersey,   and   New  York   on   the   east,  to  Indiana, 
Illinois,  and  Missouri  on  the  west.     Its  life  history 
is  as  yet  incomplete,  no  continuous  experimental 
work  having  been  done  upon  it  throughout  the 
year.     Our  miscellaneous  observations  and  breed- 
ing-cage work  give  us  thus  far  direct  evidence  of 
only  a  single  brood,  the  maggots  of  which  have 
been  seen  by  us  from  May  I7th  to  June  I3th,  the 
pupae   from    June    7th    to    i5th,   adults    emerging 
from  June  nth  to  August  7th.     It  probably  agrees 
with  other  species  of  its  genus  having  somewhat 
similar  habits  in  hibernating  as  a  winged  fly.     It  is  quite  likely  also 
that  later  broods  appear,  but  not  in  corn. 


FIG.  8. — Pupa  of 
Seed-corn  Mag- 
got; enlarged  ten 
and  one-half 
diameters. 


FIG.  9. — Fly  of  Seed-corn  Maggot ;  enlarged  eight 
and  two-thirds  diameters. 


220  BULLETIN  NO.   44.  {.May, 

THE  BLACK-HEADED  GRASS  MAGGOT. 
(Sciara,  sp.) 

When  the  spring  is  cool  and  wet  after  corn-planting,  so  that 
the  softened  seed  lies  long  in  the  ground  without  sprouting,  this 
is  especially  liable  to  certain  kinds  of  injury ;  and  it  is  under 
these  conditions  that  the  black-headed  maggot  seems  most 
likely  to  affect  it  injuriously.    Rotting  grain  is,  indeed,  un- 
doubtedly preferred  by  this  insect,  but  it  has  occasionally 
been  seen  to  infest  kernels  which  had  begun  to  grow.     It 
lives   normally   in    old  sod,    feeding   chiefly,   or  perhaps 
altogether,  on  decaying  vegetation  there,  and  will  be  found 
in  noticeable  numbers  in  corn  fields  only  where  the  field 
was  in  grass  the  preceding  year.   These  maggots  penetrate 
FIG.  io.  and  hollow  out  the  kernel,  often  leaving  nothing  more  than 
an  empty  hull.     A  score  or  more  of  them  may  infest  a  single  grain. 
They  are  also  frequently  noticed  in  rich  garden   ground  and 
among  potted  plants,  where  they  are.  accused  by  gardeners  of  eat- 
ing the  roots  and  hollowing  out  the  bulbs. 

They  are  slender,  footless,  white  maggots  (except  that  the 
head  is  jet  black),  about  a  third  of  an  inch  in  length  when  full 
grown,  and  of  nearly  uniform  diameter  throughout.  The  body  is 
soft  and  flexible,  and  the  movements  of  the  maggot  are  sluggish. 
The  species  is  very  common  throughout  the  State,  and,  doubt- 
less, throughout  the  country  at  large,  but  it  has  been  noticed  in 
its  relation  to  grass  and  corn  only  in  an  article  in  my  Thirteenth 
Report  (p.  57). 

The  larva  was  first  brought  to  my  notice  as  a  corn  insect  in 
May,  1883,  through  Dr.  Boardman  of  Stark  county,  who  forwarded 
specimens  to  my  office  with  the  information  that  this  insect  was 
destroying  newly  planted  corn  in  that  county  by  eating  out  the 
substance  of  the  germ,  sometimes  as  many  as  three  or  four  larvae 
to  a  single  kernel.  The  field  had  been  a  pasture  previously — 
partly  blue  grass  and  partly  timothy.  Other  fields  of  the  neigh- 
borhood were  abundantly  infested,  but  only  where  the  ground  had 
been  in  grass  the  preceding  year. 

May  30,  1883,  the  same  larva  was  observed  at  Towanda, 
McLean  county,  abundantly  infesting  corn  on  old  sod,  and  other 
similar  observations  were  made  to  July  io  of  that  year. 

4.  Injuries  by  six-legged  larvce  which  gnaw  or  bore  through 
the  kernel. 

The  six-legged  insect  larvae  which  infest  corn  in  the  earth  are  of 
very  unequal  importance,  the  so-called  wireworms  being  found 


I896.J         INSECT   INJURIES  TO   SEED   AND   ROOT   OF   CORN.  221 

more  injurious  to  seed  corn  than  all  other  insects  taken  together, 
the  larva  of  the  banded  Ips  being  only  occasionally  reported  to 
infest  corn  in  the  earth,  and  the  other — that  of  the  pale-striped 
flea-beetle — having  been  seen  but  once  in  this  situation.  Probably 
ninety-nine  per  cent,  of  the  six-legged  kernel-eating  insect  larvae 
will  be  found  to  be  wireworms  of  one  or  another  species ;  and  the 
greater  part  of  these  will  usually  belong,  in  Illinois,  at  least,  to  a 
single  species  which  may  well  be  called  the  corn  wireworm.  (See 
Fig.  26-29,  p.  230.) 

PALE-STRIPED  FLEA-BEETLE. 
(Systena  t<zniata>  Say.) 


FIG.  ii. — Larva  of  Pale-striped  Flea-beetle;  enlarged  nineteen  diameters. 

The  larva  of  the  pale-striped  flea-beetle  is  a  stiff,  sluggish 
insect,  slender  and  small,  less  than  a  fourth  of  an  inch  in  length 
and  about  one-eighth  as  wide,  dull,  of  a  very  pale  yellowish  color, 
minutely  roughened  and  hairy,  the  thoracic  segments  with  a  regu- 
lar geometrical  pattern  of  longitudinal  depressed  lines.  It  is  also 
distinguished  by  its  peculiar  form,  which  narrows  noticeably  from 
behind  forward,  the  head  being  very  small. 


FIG.  12. — Side  view  of  Pale-striped  Flea-beetle. 

In  the  only  case  in  which  it  was  found  infesting  growing  corn 
(Champaign,  May  17,  1886)*  the  larva  had  partly  buried  itself  in 
the  kernel  beside  the  sprout.  This  and  others  of  the  species  found 
among  the  roots  were  bred  to  the  beetle  stage  on  sprouting  corn, 
pupating  May  26th  to  June  7th  and  emerging  as  adults  on  the  I7th 
of  June.  The  great  abundance  of  this  insect  in  the  beetle  stage — so 
common  as  often  to  keep  the  leaves  of  the  cockle-bur  peppered 
with  small  holes  where  these  beetles  have  fed — makes  even  so 
slight  a  hint  of  its  capacity  for  mischief  both  interesting  and  im- 

*  See  "Canadian  Entomologist,"  1886,  Vol.  18,  p.  177;  "  Entornologica  Americana," 
Dec.,  1886,  Vol.  II.,  p.  174. 


222 


BULLETIN  NO.   44. 


{May, 


portant.  The  adult  insect  also  feeds  on  corn,  as  reported  by 
Glover  on  the  authority  of  a  correspondent,  according  to  whom 
these  bettles  nearly  destroyed  a  field  of  corn  at  Chambersburgh, 
Pa.,  eating  the  leaves  and  leaving  the  bare  stalks  standing.  The 
edges  of  the  leaves  may  be  gnawed  away,  sometimes  nothing  but 
the  midrib  being  left,  or  the  leaf  may  be  riddled  with  small  holes. 
The  agricultural  injuries  of  the  bettle  are  not  confined  to  the 
corn  plant,  however,  but  it  has  been  found  by  various  entomolo- 
gists to  feed  on  beans,  potatoes,  beets, 
clover,  strawberry  and  blackberry  leaves, 
and  the  muskmelon,  among  useful  plants, 
and  also  on  purslane,  cockle-bur,  plantain, 
ragweed  (Ambrosia),  pigweed  ( Ama- 
rantus),  and  lamb's-quarters  (Chenopo- 
dium). 

Beetles  of  this  species  have  been 
taken  by  us  at  frequent  intervals  from 
April  8  to  September  2,  much  the  most 

FIG.  i3.-Pale-striped  Flea-  abundantly  in  June  and  July.  Our  sub- 
beetle;  enlarged  ten  diameters,  stantial  knowledge  of  its  life  history  de- 
pends, however,  on  the  single  breeding  experiment  already  men- 
tioned. Four  larvae  were  collected  May  17,  1886,  and  placed  at 
once  in  breeding  cages  with  sprouting  corn.  May  26th  a  pupa  was 
found  lying  on  the  earth  in  the  cage.  Tnne  7th  another  pupa  was 
noticed  yet  in  the  earth,  and  on  the  I7th  of  June  three  adults  had 
emerged,  and  one  pupa  about  mature  was  taken  from  the  cage. 

THE  BANDED  IPS. 
(Ips fasciatus,  Oliv.). 


FIG.  14.— Larva; 

enlarged  eight 

and  one-third 

diameters. 


FIG.  15. — Pupa  ;  enlarged 
nine  diameters. 


FIG.  16.— Imago ;  enlarged  eight 
diameters. 


1896.]         INSECT  INJURIES   TO   SEED   AND   ROOT   OF   CORN.  223 

Among  the  insects  attacking  the  kernel  in  the  earth,  is  the 
larva  of  a  beetle,  which  in  the  adult  state  is  abundant  everywhere, 
feeding  upon  a  great  variety  of  vegetable  substances,  fresh  or  in  a 
state  of  decay.  The  adult  beetle  has  long  been  known  as  occasion- 
ally and  slightly  injurious  to  corn  in  the  ear ;  but  the  fact  that  the 
larva  may  infest  seed  corn  after  planting,  although  first  noted  by 
us  in  1883,  has  not  hitherto  been  published. 

My  first  observation  to  this  effect  was  made  at  Normal,  111., 
June  i8th  of  the  above  year.  In  a  field  of  corn  a  part  of  which  had 
been  in  pasture  for  fifteen  years  preceding,  while  the  remainder 
had  grown  turnips  the  year  before — which,  however,  had  not  been 
removed  from  the  ground — large  numbers  of  these  larvae  were 
found  in  and  about  the  seed  kernels.*  From  the  first,  stalks  were 
growing  fully  two  inches  high.  Occasionally  a  larva  was  seen  in 
the  space  between  the  rows,  but  nearly  all  were  concentrated  in 
the  hills  of  corn.  Considering  the  ordinary  habit  of  the  species, 
it  is  quite  likely  that  the  beetles  were  attracted  to  this  field  by 
rotten  turnips  remaining  in  the  ground. 

June  16,  1885,  larvae  were  very  abundant  at  Mt.  Pulaski,  in 
central  Illinois,  in  the  kernels  of  ears  left  in  the  field  which  had 
been  turned  under  by  the  plow  and  had  commenced  to  grow. 
May  16,  1887,  a  number  were  taken  in  a  similar  situation  from  a 
mass  of  sprouting  corn  at  Urbana,  111. 

As  an  adult,  this  species  was  reported  by  Walsh  in  1867,  on 
the  testimony  of  an  anonymous  correspondent,  to  have  done  an 
extensive  injury  some  years  before  to  sweet  corn  in  Minnesota 
by  burrowing  in  the  ear;  and  Dr.  John  Hamilton,  of  Toronto, 
Canada,  says  that  it  is  often  found  in  the  green  ears  of  maize,  but 
only  in  such  as  have  been  injured  by  birds  or  other  animals.  Sep- 
tember 13,  1893,  it  was  brought  to  my  office  by  an  assistant,  Mr. 
Marten,  with  several  injured  kernels  of  corn,  from  the  exposed  tip 
of  the  ear,  which  the  beetle  had  burrowed  into  or  eaten  away 
irregularly.  In  one  other  case  reported  under  this  same  date  it 
was  found  burrowing  into  doughy  grains  beneath  the  husk,  more 
than  an  inch  from  the  nearest  exposed  kernels,  the  natural  infer- 
ence being  that  the  grains  had  not  been  previously  injured.  This 
very  common  species  must  consequently  be  classed  as  one  of  the 
minor  insect  enemies  of  corn,  which  it  injures  both  as  larva  and 
adult — much  more  seriously,  "however,  in  the  former  stage. 

The  feeding  habits  of  the  larva  are  very  much  less  known. 
Our  own  notes  show,  besides  its  occurrence  in  corn,  that  it  breeds 
in  rotten  apples.  The  species  appears  from  our  observations  to 

*The  field  had  been  twice  planted  because  of  a  partial  failure  of  the  first  seed,  and 
the  kernels  of  both  plantings  were  infested. 


224  BULLETIN   NO.   44.  \May, 

hibernate  as  an  adult,  and  to  give  origin  during  the  year  to  at  least 
two  generations.  The  larva  enters  the  earth  to  transform,  making 
a  friable  earthen  cell. 

WlREWORMS. 

Failure  of  the  seed  to  start,  or  a  sudden  withering  of  the  corn 
plant  when  a  foot  or  two  in  height,  especially  if  the  field  was 
broken  up  from  grass  one  or  two  years  preceding,  are  always 
sufficient  to  warrant  a  suspicion  of  injury  by  wireworms.  These 
hard,  smooth,  shining,  reddish  or  yellowish  brown  cylindrical  six- 
legged  larvae*  are  indeed  much  more  destructive  to  seed-corn, 
under  ground,  in  Illinois  than  all  other  insects  taken  together. 
They  may  begin  their  injuries  to  the  seed  almost  immediately 
after  planting,  commonly  burying  their  heads  in  it  at  first,  some- 
times eating  entirely  through  the  kernel,  and  even  devouring  it 
completely.  If  they  attack  the  growing  plant  they  are  likely  to 
eat  the  smaller  roots,  or  to  penetrate  or  bore  through  the  larger 
ones,  dwarfing  or  killing  the  corn  ;  and  later,  when  the  young  plant 
is  several  inches  high,  they  frequently  kill  it  outright  by  boring 
their  cylindrical  channels  directly  through  the  underground  part 
of  the  stalk.  They  are  far  the  commonest  in  corn  on  ground 
which  has  lain  for  several  years  in  grass,  and  are  much  more  likely 
to  do  serious  mischief  the  second  year  after  the  breaking  up  of  the 
sod.  They  should  be  sought  for  diligently  on  such  lands  whenever 
the  seed  fails  to  grow,  or  when  the  sudden  withering  of  the  plant 
hints  at  a  serious  damage  to  it  under  ground.  At  such  times  practi- 
cally all  the  wireworms  in  the  field  will  be  found  in  the  hills  of 
corn  or  in  their  immediate  vicinity,  sometimes  as  many  as  ten  or 
a  dozen  in  each  hill. 


FIG.  17. — Larva  of  Drasterius  elegans;  enlarged  seven  diameters. 

Although  wireworms  are  rarely  distinguished  by  farmers  as  of 
different  kinds,  there  are  no  less  than  one  hundred  species  of  these 
insects  known  to  occur  in  Illinois  in  the  adult  or  beetle  stage, 
and  eight  species  of  the  larvae  (the  so-called  "wireworms"  them- 
selves) have  been  found  by  us  here  injurious  to  corn.  These  corn 
wireworms  have,  however,  so  strong  a  family  resemblance  that 

*This  general  description  of  the  wireworms  does  not  apply   to  one  very  peculiar 
form  (Cardiophorus),  taken  by  us  but  once  in  Illinois. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  22$ 

they  are  little  likely  to  be  confused  with  any  other  insect  by  the 
fairly  good  observer  who  has  once  learned  to  recognize  any  one 
of  them.  They  vary  in  length,  when  full  grown,  from  half  an  inch 
to  an  inch  and  a  quarter,  but  agree  in  their  hard,  crust-like  surface, 
nearly  destitute  of  hairs;  their  brownish  color,  varying  from 
yellowish  to  reddish ;  their  slender  bodies,  distinctly  segmented, 
and  of  about  equal  diameter  throughout  their  length ;  their  flat- 
tened heads,  with  jaws  borne  in  front  and  extending  horizontally 
forward ;  the  six  pairs  of  short,  stout,  jointed  legs  on  the  three 
segments  following  the  head ;  the  absence  of  legs  of  any  kind  on 
the  eight  segments  thereafter;  and  the  single  sucker-like  proleg 
on  the  under  surface  of  the  last  segment  of  the  body — the  thir- 
teenth, counting  the  head  as  one.  This  terminal  segment  is  often 
peculiarly  finished  above — concave  or  convex,  notched,  toothed, 
or  lobed  at  the  sides  and  end,  or,  in  one  species,  with  a  pair  of 
conspicuous  round  openings  on  the  upper  surface.  Taken  in  the 
fingers,  the  wireworms  bend  and  wriggle  with  surprising  strength, 
and  easily  slip  out  of  the  grasp. 

They  live  regularly  and  normally  in  grass  lands,  feeding  on 
roots  of  grass,  where,  however,  their  numbers  are  rarely  sufficient 
to  produce  any  notable  effect  upon  the  sod.  It  is  only  when  con- 
centrated in  the  comparatively  scanty  vegetation  of  a  field  of 
young  corn  in  spring,  or  occasionally 
in  young  wheat  or  other  small  grain, 
that  they  do  any  very  marked  or  im- 
portant harm.  They  are  to  be  found 
in  grass  of  every  description,  from 
prairie  sod  and  the  coarse  and  rank 
sedges  along  the  borders  of  marshes, 
to  the  cultivated  grass  of  our  pastures 
and  meadows. 

The  commonest  form  of  attack  on 
the  corn,  as  seen  by  the  farmer,  is, 
perhaps,  the  burrowing  of  the  worm 
into  the  seed  kernel,  either  before  or 
after  it  has  sprouted.  All  the  species 
treated  in  this  paper  have  been  seen 
with  their  heads  buried  in  the  kernels,  FlG.  l8._zv«/^  «/*«*.  beetle; 

either  in  the  field  or  in  breeding-cages,      enlarged  seven  and  ahalf  diameters. 

Frequently  attacks  in  the  field  have  been  so  severe,  particularly 
the  first  or  second  year  after  the  sod  has  been  broken,  as  to 
require  planting  a  second  or  third  time.  Drasterius  elegans  (Fig. 
17  and  1 8)  and  Melanotus  fissilis  have  been  taken  in  the  act  of  per- 
forating stalks  just  above  the  root.  In  a  field  at  Peru,  Illinois, 


226 


BULLETIN  NO.  44. 


{May, 


examined  July,  1883,  as  much  as  six  per  cent,  of  the  corn  in  the 
field  had  been  killed  in  this  way,  sometimes  two  or  three  larvae 
being  found  in  a  single  stem. 


FIG.  19. — Cardiophorus  sp.,  larva,  dorsal  view  ;  enlarged  four  diameters 

The  roots  of  the  corn  are  also  eaten  to  a  greater  or  less  extent 
by  all  the  species,  the  damage  from  this  cause  being  sometimes 
quite  considerable.  .A  field  in  Alexander  county  visited  in  June, 
1886,  had  spots  of  one  hundred  to  two  hundred  hills  not  more  than 
a  foot  high,  while  the  balance  of  the  field  was  four  or  five  feet 
high.  Many  hills  in  these  spots  were  gone.  In  the  smaller  hills 
many  small,  slender,  peculiar-looking  larvae  of  an  unknown  species 
of  Cardiophorus  were  found.  (Fig.  19.)  In  some  instances  they 
had  almost«completely  destroyed  the  roots  of  the  corn  ;  in  others 
the  roots  were  bored  through  and  the  outer  surface  eaten  away  so 
a?  to  almost  destroy  their  usefulness. 


FIG.  20. — Wheat  Wireworm  ;  enlarged  five  diameters. 

Agriotes  mancus  is  so  destructive  to  wheat  as  to  be  known  as 
the  "wheat  wireworm  "  (Fig.  20,  21,  and  22).  Drasterius  elegans 
is  also  known  to  infest  this  crop,  as  do  other  species  as  well.  Rye, 
barley,  and  oats  also  suffer  from  wireworm  attacks.  Dr.  Fitch 
also  found  them  burrowing  in  timothy  bulbs.  Wireworms  taken 
from  a  dense  clover  sod  and  placed  in  our  breeding-cages,  where 
they  were  supplied  only  with  grass  and  clover,  gave  us  images  of 
Asaphes  decoloratus.  (Fig.  23,  24,  and  25.) 


FIG.  21. — Side  view  of  Wheat  Wireworm. 


Among  root  crops,  potatoes  often  suffer  from  being  bored  into 
and  by  having  the  surface  gnawed  and  corroded  by  the  worms  ; 
but  turnips,  it  is  said,  appear  to  be  more  infested  by  them  than  any 
other  root  crop. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  22; 

Besides  the  crops  already  mentioned  Dr.  Fitch  names  the  fol- 
lowing, which  the  wireworms  are  known  to  attack  or  are  recorded 
as  attacking:  mangel-wurzel,  cabbage,  carrots,  beets,  onions, 
lettuce,  rape,  hops,  strawberries,  pinks,  carnations,  dahlias,  lobelias, 
and  numerous  other  garden  flowers.  They  have  also  been  reported 
to  me  by  a  horticultural  friend  as  destroying  planted  peach  pits  in 
the  earth. 

GENERAL   STATEMENT   OF   LIFE   HISTORIES. 

The  injurious  species  agree  fairly  well  in  the  main  features  of 
their  life  history,  changing  to  the  dormant  pupae  in  the  earth  in 
July  or  sometimes  in  August,  and  changing  again  some  three  or 
four  weeks  later  to  the  brown  or 
reddish  beetles  commonly  known 
as  "click  beetles"  or  "jumping- 
jacks" — hard,  somewhat  hairy  in- 
sects, of  slender  oval  form,  distin- 
guished at  once  by  their  peculiar 
habit  of  springing  into  the  air  with 
a  sudden  click  when  placed  upon 
their  backs.  A  large  part  of  these 
fully  developed  beetles  remain  un- 
der ground  until  spring,  enjoying 
there  the  protection  of  the  oval 
earthen  cavity  or  cell  formed  by  the 
larva  as  a  preparation  for  pupation. 
A  part,  however,  come  forth  from 
the  ground  in  fall,  passing  the  winter 

in     sheltered     places,     and     the    re-  FlG-  22.— Beetle  of  Wheat  Wireworm ; 
,  ....  enlarged  seven  diameters. 

mamder  emerge   in    spring,  laying 

their  eggs  most  commonly  in  grass  lands  in  the  earth.  "Of  their 
subsequent  life  history  little  is  yet  definitely  known.  It  seems 
certain  that  all  live  more  than  one  year  as  wireworms  in  the  earth, 
and  observation  of  the  various  sizes  of  larvae  of  the  same  species 
to  be  found  in  the  field  at  once,  usually  supports  the  common  im- 
pression that  the  period  of  life  in  the  larval  stage  does  not  extend 
beyond  two  years  ;  a  fact  which,  taken  in  connection  with  the 
death  and  decay  of  grass  roots  the  first  year  after  breaking  up  the 
sod,  serves  to  explain  the  greater  damage  done  by  wireworms  the 
second  year  the  ground  is  in  corn.  The  number  of  wireworms 
having  been  little  diminished  since  the  crop  was  changed,  and 
their  original  food  having  practically  disappeared,  they  are  com- 
pelled to  concentrate  upon  the  corn — either  the  newly  planted  seed 
or  the  young  plant  while  it  is  still  very  small. 


228  BULLETIN  NO.   44.  [May, 

NATURAL   ENEMIES   OF   WIREWORMS. 

Only  a  single  parasitic  fly  has  been  bred  by  us  from  wireworms. 
Comstock  and  Slingerland  frequently  found  them  killed  in  their 
breeding-cages  by  a  fungus  determined  by  Professor  Roland 
Thaxter  as  probably  Metarrhizius  anisoplice.  Those  killed  by  this 
disease  have  the  body  filled  by  the  growth  of  the  fungus,  and 
assume  a  woody  appearance.  An  Asaphes  larva  turned  out  by  the 
plow  at  Champaign  May  10,  1886,  was  infested  by  a  parsitic  fungus 
of  another  genus,  very  much  like  Cordiceps. 


FIG.  23. — Larva  of  Asaphes  decoloratus;  enlarged  three  and 
three-fourths  diameters. 

•  In  my  work  on  the  food  of  birds,*  I  found  that  some  seven- 
teen species  eat  to  some  extent  "click  beetles,"  or  their  larvae,  the 
wireworms.  These  insects  constitute  about  two  per  cent,  of  the 
food  of  five  species  of  the  thrush  family — the  robin,  and  the  brown, 
the  hermit,  the  wood,  and  the  Alice  thrushes.  The  examination 
of  the  food  of  these  birds  continued  throughout  the  year,  and  the 
proportionate  amount  of  these  beetles  eaten  was  found  to  be 
greatest  during  the  months  when  they  were  most  numerous;  but 
even  then  the  quantity  destroyed  was  scarcely  sufficient  to  affect 
materially  their  average  numbers.  Mr.  E.  V.  Wilcox,t  while 
studying  the  food  of  the  robin,  at  the  Ohio  Agricultural  Experi- 
ment Station,  found  in  the  stomachs  of  twenty-seven  of  these 
birds,  shot  in  April  and  May,  "click  beetles"  amounting  to  three 
and  one-half  per  cent,  of  their  food.  Of  the  remaining  species  of 
birds  known  to  eat  them,  none  take  enough  to  make  more  than  a 
fraction  of  one  per  cent,  of  their  food,  except,  perhaps,  the  crow. 
Dr.  Fitch  says  that  "wireworms  and  their  progenitors,  the  snap- 
ping beetles,  constitute  the  favorite  food  and  principal  sustenance 
of  these  birds  [crows]. "f 

*  Bull.  111.  State  Lab.  Nat.  Hist.,  Vols.  I  and  II. 

t  Bull.  Ohio  Agr.  Exper.  Station,  No.  43,  (1892),  p.  127. 

j  Eleventh  Rep.  (Trans.  N.  Y.  State  Agr.  Soc.,  (1866),  p.  542. 


1896.]         INSECT  INJURIES  TO  SEED  AND   ROOT  OF  CORN.  22Q 


FIG.  24. — Last  segment  of 

larva  of  Asaphes  decoloratus; 

much  enlarged. 


FIG.  25. — Beetle  of  Asaphes 

decolor atus;  enlarged  four  and 

a  fifth  diameters. 


PREVENTION  AND   REMEDY. 

Probably  no  class  of  agricultural  insects  has  had  prescribed  for 
it  a  longer  list  of  artificial  remedies  than  the  wireworms,  and  cer- 
tainly no  such  list  has  been  of  less  practical  value.  After  many 
generations  of  experience  with  their  work  in  this  country  and  in 
Europe  their  injuries  continue  at  present  practically  unchecked  by 
any  treatment  consistent  with  the  methods  of  American  agriculture. 

Even  poisons  of  the  most  deadly  sort  applied  to  corn  previous 
to  planting,  or  to  food  lures  distributed  through  the  ground  for  the 
purpose  of  drawing  off  the  attention  of  these  insects  from  corn, 
have  proved  almost  entirely  valueless,  both  in  my  experience  and 
in  the  more  elaborate  trials  made  by  Comstock  and  Slingerland  in 
New  York.  Late  fall  plowing,  breaking  open  the  pupal  chambers 
within  which  the  recently  transformed  adults  pass  the  winter,  will 
probably  have  the  effect  to  diminish  generally  the  number  of 
these  beetles  during  the  following  year.  Comstock  and  Slinger- 
land have  also  ascertained  that  the  adult  beetles  are  susceptible  to 
certain  poisons  judiciously  distributed  with  certain  attractive  kinds 
of  food ;  and  I  have  to  suggest  a  systematic  rotation  intended  to 
interpose  between  grass  and  corn  a  crop  not  vulnerable  to  the 
wireworms.  Otherwise  we  are  substantially  without  a  hint  of  any 
means  of  diminishing  the  ravages  of  these  insects  other  than  the 
time-honored  resource  of  the  corn  farmer,  namely,  late  planting  of 
his  corn  the  second  year  after  sod,  and  late  replanting  if  the  first 
planting  is  destroyed.  In  the  latter  case  it  is  well  to  plant  between 
the  rows,  allowing  the  first  corn  to  stand  as  long  as  is  consistent 
with  a  proper  cultivation  of  the  field.  All  the  wireworms  being  at 


230 


BULLETIN  NO.  44. 


\May, 


the  time  concentrated  in  the  old  hills  of  corn,  if  these  be  destroyed 
when  the  field  is  planted  the  second  time,  the  wireworms  still 
active  in  the  earth  are  forced  to  attack  the  freshly  planted  kernels 
as  their  only  food  resource. 


FIG.  26. — Corn  Wireworm ;  enlarged  four  diameters. 

The  first  experiments  with  poisons  for  the  wireworms  of  which 
we  have  definite  record,  were  made  at  my  office  in  1885,  and 
reported  briefly  in  my  "Miscellaneous  Essays  on  Economic  Ento- 
mology" (p.  18),  printed  the  following  year. 


=s        A 


FIG.  27. — Side  view 

of  a  middle  seg- 
ment of  Corn  Wire- 


FIG.  28. — Last  segment, 

dorsal  view  ;  greatly 

enlarged. 


FIG.  29. — Beetle  of 

Corn  Wireworm  ; 

enlarged  four  and  a 

half  diameters. 


Later,  in  May,  1888,  we  fed  thirty-seven  wireworms  on  corn 
soaked  for  seven  days  in  a  mixture  of  water  and  Paris  green. 
The  corn  was  covered  with  a  coating  of  the  green  poison,  and  was 
eaten  freely  by  some  of  the  worms  without  killing  them.  Twelve 
wireworms  fed  on  corn  soaked  in  Fowler's  solution  diluted  with  an 
equal  quantity  of  water  were  not  affected,  although  a  portion  of 
the  corn  was  eaten.  Twelve  others,  fed  on  corn  soaked  in  an 
alcoholic  solution  of  arsenic,  were  not  injured  by  the  poison, 
though  feeding  freely  on  the  corn.  Experiments  in  June  and 
July,  when  wireworms  were  fed  on  corn  soaked  in  a  solution  of 
arsenic  in  boiling  water,  were  less  satisfactory  because  the  larvae 
were  so  near  pupation  that  they  ate  little  or  none,  pupal  cells 


1896.]        INSECT  INJURIES  TO  SEED  AND  ROOT  OF  CORN.  231 

being  formed  five  days  after  the  experiment  began.  Corn  soaked 
in  a  solution  of  strychnine — four  grains  to  a  half  pint  of  water — 
over  night,  and  fed  to  seven  wireworms  June  28,  1888,  had  not 
affected  them  by  July  5th,  although  the  corn  was  slightly  eaten. 
Twelve  worms  supplied  with  corn  soaked  twenty-four  hours  in  an 
alcoholic  solution  of  corrosive  sublimate  June  27,  1888,  did  not  eat 
the  corn. 

A  repetition  of  these  experiments  in  June  and  July,  1891,  by 
a  different  assistant  and  under  somewhat  different  conditions, 
gave  substantially  the  same  results.  June  27,  1891,  corn  was 
soaked  in  a  saturated  solution  of  potassium  cyanide  and  fed  to 
three  wireworms.  July  3d  one  grain  of  corn  was  slightly  eaten, 
and  July  roth  one  grain  was  badly  eaten  and  one  worm  missing — 
probably  eaten  by  mice  that  had  obtained  access  to  the  cage. 
July  2Oth  several  grains  were  badly  eaten;  July  27th  the  remaining 
two  worms  were  active,  but  the  corn  was  untouched;  and  the 
experiment  ended  without  effect. 

In  many  of  the  experiments,  particularly  when  alcoholic  solu- 
tions were  used,  or  where  the  corn  was  soaked  for  a  considerable 
length  of  time  in  arsenical  solutions,  it  failed  entirely  to  germinate  ; 
while  in  experiments  where  the  grain  was  simply  wet  and  rolled  in 
the  arsenites,  or  soaked  for  only  a  few  hours,  it  grew  almost  as 
freely  as  did  untreated  corn  in  check  lots. 


FIG.  31. — Side  view  of  a  middle 
segment  of  larva  of  same  species, 
showing  muscular  impression,  spira- 
cle, etc. 


FlG.  30. — Beetle  of  Melanotus   com- 
munis;  enlarged  four  diameters. 


FIG.  32. — Last    segment  of  same, 
dorsal  view  ;  greatly  enlarged. 


232  BULLETIN  NO.  44.  \May, 

These  experiments  with  the  arsenical  poisons  and  strychnine 
agree  substantially  with  those  of  Messrs.  Comstock  and  Slinger- 
land,  published  in  November,  1891,  and  show  that  it  is  not  practi- 
cable to  protect  the  corn  by  means  of  them,  even  were  it  possible 
to  use  them  without  retarding  or  preventing  the  germinating  of 
the  seed. 

Coating  the  kernels  with  tar  and  soaking  them  in  a  solution 
of  salt,  a  solution  of  copperas,  a  solution  of  chloride  of  lime  and 
copperas,  in  spirits  of  turpentine,  and  in  kerosene  oil,  have  been 
tried  by  Comstock  and  Slingerland  without  encouraging  results. 

Applications  of  kerosene  emulsion  and  pure  kerosene  made  to 
the  worms  in  the  earth  were  found  by  me  in  1885  practically 
ineffective,  any  strength  sufficient  to  kill  the  larv.ne  killing  vegeta- 
tion also.  Similar  results  were  obtained  by  Comstock  and  Slinger- 
land, who,  after  using  crude  petroleum,  an  emulsion  of  the  same, 
and  a  common  kerosene  emulsion,  concluded  that  the  last  is  more 
promising  than  the  others,  but  that  it  cannot  be  profitably  applied  on 
a  large  scale.  Experiments  made  by  them  show  also  that  even  a 
clean  fallow  for  an  entire  season  will  not  starve  out  the  worms; 
that  neither  buckwheat,  mustard,  nor  rape  crops — frequently 
recommended  to  clear  the  earth  of  wireworms — will  accomplish 
the  desired  result;  and  that  salt  applied  at  the  rate  of  1,600  pounds 
to  the  acre — a  heavy  dressing — neither  drives  the  wireworms 
deeper  into  the  soil  nor  causes  them  to  migrate  to  any  appreciable 
distance ;  that  kainit  used  as  a  fertilizer,  even  in  very  large  quanti- 
ties, had  little  effect  if  any  on  the  wireworms;*  that  muriate  of 
potash — four  to  six  tons  to  the  acre  (an  excessive  amount) — is  but 
slightly  effective ;  that  lime  at  the  rate  of  even  two  hundred 
bushels  per  acre  does  not  injure  wireworms ;  that  chloride  of 
lime  must  be  used  in  impracticable  quantity  to  produce  any 
marked  effect ;  and  that  gas-lime,  although  capable  of  destroying 
the  wireworms,  must  be  applied  in  such  great  quantities  that  its 
use  is  impracticable  on  large  areas.  Bisulphide  of  carbon  poured 
into  a  hole  in  the  earth  near  the  infested  hill  destroys  the  wire- 
worms,  but  at  an  excessive  cost. 

The  most  promising  remedy  for  wireworms,  in  my  judgment, 
is  one  which  has  unfortunately  not  been  experimentally  tested, 

*These  results  are  inconsistent  with  those  reported  by  Prof.  J.  B.  Smith  in  the  I2th 
Ann.  Rep.  N.  J.  Agr.  Exper.  Station  (for  the  year  1891),  p.  412.  Here  Professor  Voor- 
hees,  Chemist  of  the  Station,  is  said  to  have  applied  kainit  and  muriate  of  potash  sepa- 
rately to  two  sections  of  a  fourteen-acre  piece  of  corn  on  ground  always  badly  infested 
by  wireworms  and  cutworms,  leaving  a  strip  between  these  sections  without  treatment. 
Care  was  taken  that  the  sections  should  be  similar  with  respect  to  quality  of  land,  situa- 
tion, etc.  As  a  consequence,  the  kainit  section  was  reported  as  almost  entirely  exempt 
from  injury  by  insects,  the  muriate  section  as  but  little  infested,  and  the  intermediate 
strip  as  almost  destroyed.  It  is  evident  from  the  context  that  this  experiment  had  been 
made  some  years  before,  apparently  not  under  the  inspection  of  an  entomologist. 


l8g6.J        INSECT  INJURIES  TO  SEED  AND   ROOT  OF  CORN.  233 

but  which  is,  nevertheless,  precisely  based  upon  our  knowledge  of 
the  life  history,  food,  and  habits  of  these  insects.  It  consists  of  a 
rotation  in  which  clover  follows  always  upon  grass  and  is  itself 
followed  by  corn.  According  to  this  plan  pastures  and  meadows 
of  grass  might  lie  unchanged  for  several  years,  being  plowed,  when 
broken  up,  in  late  summer  or  early  fall  and  sown  to  clover  in  the 
spring — either  with  oats,  or  on  winter  wheat  or  rye  sown  the  fall 
before.  The  clover  should  be  allowed  to  stand  a  second  year,  and 
might  then  be  followed  with  corn  with  positive  assurance  that  the 
wireworms  originally  in  the  sod  would  by  that  time  have  entirely 
disappeared.  From  the  regular  rotation  for  grain  lands,  grass 
would  be  thus  excluded.  In  such  a  rotation  corn  might  be  fol- 
lowed by  small  grain,  this  by  clover,  and  this  by  corn.  While  the 
wireworms  might  produce  some  visible  effect  on  the  small  grain 
the  first  year  after  grass,  this  would  usually  be  much  less  serious, 
at  any  rate,  than  the  damage  to  corn. 

The  general  entomological  effect  of  some  such  management 
could  not  fail  to  be  beneficial,  since  it  would  apply  to  cutworms 
and  white  grubs  as  well  as  to  the  wireworms  now  under  discussion. 
The  system  of  rotation  now  common  in  central  Illinois  is,  indeed, 
seriously  defective  in  the  fact  that  the  plants  composing  it — Indian 
corn,  small  grains,  and  grasses — are  all  of  the  same  botanical 
family  and  consequently  subject  in  large  measure  to  the  same 
enemies.  Any  variation  of  this  system  which  will  introduce  as  a 
regular  link  in  the  chain  a  crop  belonging  to  some  other  and  widely 
different  family  of  plants,  will  serve  the  general  purpose  of  that 
here  proposed. 

B.     DETAILED  DISCUSSION  OF  INJURIES  TO 
THE  ROOTS. 

Injury  to  the  roots  of  corn  in  spring  and  early  summer  may 
be  indicated  to  the  close  observer  by  the  aspect  of  the  growing 
crop.  If  the  corn  fails  to  appear  in  spring,  the  difficulty  may  not 
be  due  to  poor  seed  or  to  injuries  to  the  kernel,  but  may  be  caused 
by  an  early  insect  attack  upon  the  young  roots,  which  may  even 
kill  the  plant  outright  before  the  sprout  has  broken  ground.  The 
root  louse  of  the  corn  and  the  wireworms  are  most  likely  to  be 
concerned,  in  this  form  of  injury. 

Later  in  the  season,  when  the  plant  is  a  few  inches  high,  the 
uneven  growth  of  the  corn  will  often  attract  attention,  patches 
here  and  there  advancing  slowly  in  comparison  with  parts  of  the 
field  adjacent,  and  in  a  way  not  to  be  accounted  for  by  differences 
of  soil.  In  such  cases,  white  grubs,  wireworms,  corn-root  worms, 


234  BULLETIN  NO.  44.  [May, 

or  plant  lice  should  be  sought  for.  Combined  with  this  uneven 
growth,  or  possibly  in  times  of  drouth  without  it,  the  farmer  may 
notice  yellow  patches  in  his  field,  the  color  being  most  pronounced 
upon  the  lower  leaves.  The  root  louse  of  the  corn  will  be  found 
responsible  in  most  cases  for  this  partial  discoloration,  but  any  of 
the  species  just  mentioned  may  produce  a  similar  effect,*  or  it 
may  be  caused  on  the  lower  part  of  the  stalk  by  the  chinch  bug. 

An  especially  significant  symptom  of  more  or  less  serious 
mischief  is  the  presence  in  the  field  of  numerous  burrows  of  ants, 
commonly  placed  in  or  immediately  near  the  hills  of  corn,  and 
most  conspicuous  shortly  after  rains.  This  invariably  indicates  the 
presence  of  root  lice  in  the  field,  although  if  the  corn  be  small  a 
careful  search  may  fail  to  detect  them  at  the  time.  The  nature  of 
the  association  between  the  ants  and  the  root  lice  is  such  that  the 
former  prepare  the  way  for  the  latter  early  in  the  season  by  sink- 
ing their  burrows  among  the  corn  roots,  thus  giving  the  lice  access 
to  them. 

If  at  about  the  time  the  ear  is  beginning  to  form,  and  from 
that  time  onward,  the  stalks  of  corn  are  easily  prostrated  by  wind 
and  rain,  and  do  not  readily  rise  again,  it  will  commonly  be  found 
that  the  hold  of  the  plant  upon  the  earth  is  abnormally  slight,  so 
that  the  hill  may  be  pulled  up  too  easily.  This  condition  of  the 
plant  is  due  to  a  loss  of  roots,  usually  to  be  attributed  to  one  of 
the  corn  root  worms,  or,  more  rarely,  to  the  white  grubs.  Some- 
times, however,  a  similar  appearance  is  given  late  in  the  season  to 
a  field  infested  by  the  chinch  bug,  which  by  abstracting  sap  from 
about  the  base  of  the  stalk  just  beneath  the  surface  of  the  ground 
will  often  prevent  the  shooting  forth  of  the  so-called  "brace- 
roots,"  which  serve  to  anchor  the  top-heavy  stalk  more  firmly  in 
the  earth. 


*  A  condition  of  the  corn  very  similar  to  that  just  described  is  not  due  to  insect 
attack  at  all,  but,  as  is  supposed,  to  a  bacterial  disease  of  the  roots  known  as  the  corn 
root  blight,  fully  described  by  Prof.  T.  J.  Burrill  in  Bulletin  No.  6  of  the  Illinois  Agri- 
cultural Experiment  Station  (August,  1889).  In  this  disease  the  corn  stops  growing  in 
.patches,  becoming  yellow  and  usually  slender,  and  sometimes  dying  while  young.  The 
yellow  color  is  most  pronounced  upon  the  lowest  leaves.  On  pulling  up  the  plant,  the 
oldest  and  the  lowest  roots  are  seen  to  be  injured  and  usually  dead,  the  bottom  part  of 
the  stalk  to  which  these  roots  are  attached  being  similarly  affected.  If  split  through  the 
middle,  the  inner  tissue  of  this  lower  part  is  seen  to  be  of  a  uniform  darker  color,  and  a 
slight  discoloration,  becoming  less  and  less  pronounced  above,  appears  in  the  next 
succeeding  joints,  while  the  parts  between  them  are  seemingly  healthy.  On  the  sur- 
face, when  carefully  cleared  of  dirt,  brownish  corroded  spots  may  be  found,  sometimes 
covered  with  a  firm  gelatinous  material. 


1896.]         INSECT  INJURIES  TO   SEED  AND  ROOT  OF  CORN.  235 

i .  Some  of  the  roots  deadened,  hardened,  or  dwarfed,  without 
loss  of  substance. 

a.  Small  brown  or  yellowish  ants  abundant  in  the  hills, 
and  very  small,  bluish  green  or  whitish,  oval,  thick- 
bodied  root  lice  on  the  larger  roots. 

PLANT  LICE  AND  MEALY  BUGS. 
(APHIDID.E  AND  COCCID.E.) 

.  Associated  with  ants  in  hills  of  corn,  the  observer  may  find 
any  one  or  more  of  eight  species  of  minute,  soft,  thick-bodied, 
six-legged  insects,  sometimes  winged,  but  usually  without  wings, 
and  always  of  very  sluggish  habit  and  slight  power  of  locomotion. 
When  exposed,  they  may  show  little  or  no  signs  of  disturbance, 
but  if  shaken  off  the  roots  into  which  their  stout  jointed  beaks  are 
thrust,  they  will  probably  crawl  slowly  and  clumsily  about,  making 
movements  almost  too  sluggish  and  aimless  to  look  like  efforts  to 
escape.  The  ants  which  have  nested  in  the  hill  will,  however, 
commonly  seize  these  little  insects  in  their  mandibles  and  hurry 
away  with  them  into  concealment. 

By  far  the  greater  part  of  those  answering  to  the  above 
description  to  be  found  in  the  corn  field,  will  usually  be  plant  lice 
(aphides);  and  will  mostly  belong,  in  fact,  to  a  single  species,  the 
corn  root  aphis;  but  a  few  may  be  "mealy  bugs"  (genus  Dactylo- 
pius,  family  Coccidae),  recognizable  as  such  by  their  general 
resemblance  to  the  kinds  of  "mealy  bugs"  common  in  green- 
houses. They  may  be  readily  distinguished  from  the  plant  lice  by 
their  thicker,  clumsier  bodies,  and  by  the  almost  rudimentary  size 
of  their  legs  and  antennae.  They  are  always  covered  with  a  mealy 
or  powderly  excretion  of  minute  particles  of  wax,  and  never  have 
honey  tubes,  or  cornicles,  on  the  back  of  the  abdomen — both, 
however,  characters  in  which  they  agree  with  some  of  the  lower 
plant  lice.  From  all  the  corn-infesting  plant  lice  they  may.  be 
technically  separated  by  the  fact  that  their  tarsi  are  single  jointed, 
and  bear  but  a  single  tarsal  claw,  while  the  plant  lice  of  this  group 
have  two  tarsal  joints  and  a  pair  of  tarsal  claws. 

Plant  lice  are  among  the  most  prolific  of  insects,*  producing 
several  generations  annually,  but  they  are  commonly  held  severely 
in  check  by  climatic,  meteorological,  and  biological  conditions; 
that  is,  by  season,  weather,  and  plant  or  animal  parasites.  They 

*Slingerland  has  bred  twenty-five  generations  of  a  plant  louse  {Myzus  ac/iyrantes?) 
in  a  single  year  (Science,  Vol.  XXI.,  1893,  p.  48);  and  Buckton  shows  (A  Monograph  of 
British  Aphides,  Vol.  I.,  p.  80)  that  a  single  rose  aphis  (Sip/ionophora  rosce)  might  give 
origin,  at  its  normal  rate  of  unchecked  multiplication,  to  over  thirty-three  quintillions  of 
plant  lice  in  a  single  season,  equal  in  weight  to  more  than  a  billion  and  a  half  of  men. 


236  BULLETIN  NO.  44.  [May, 

are,  consequently,  capable  of  rapid  and  enormous  increase  when 
any  of  these  checks  are  temporarily  weakened  to  any  considerable 
degree.  As  they  affect  the  plant  by  abstracting  the  elaborated 
sap  upon  which  its  vital  activity  depends,  the  injury  done  is  usually 
general,  and  especially  is  this  true  if  the  root  be  the  part  infested. 
Some  species,  however,  in  addition  to  this  general  drain  upon  the 
life  of  the  plant,  cause  a  distinct  local  deformity  to  root  or  leaf  in 
the  nature  of  a  gall,  which  protects  them  at  the  same  time  that  it 
secures  them  food.  Any  crop  liable  to  their  attack  in  force  is 
never  long  free  .from  danger,  but,  on  the  other  hand,  a  seemingly 
irresistible  outbreak  may  disappear  as  quickly  as  it  came,  a  slight 
and  almost  imperceptible  change  of  conditions  often  taking  tre- 
mendous effect  on  these  delicate  insects.* 

Economically,  plant  lice  may  be  divided,  according  to  the 
peculiarities  of  their  life  histories,  into  several  groups  or  classes. 
Some  generation,  or  some  part  of  some  generation,  may  grow 
wings,  fitting  them  for  rapid  dissemination,  or  the  species  may  be 
without  winged  representatives.  They  may  live  through  the  whole 
season  of  their  active  life  above  ground,  on  exposed  parts  of  the 
plant;  they  may  spend  the  whole  season  under  ground,  upon  the 
roots;  or  they  may  alternate,  spreading  each  year  from  roots  to  stalk 
and  leaves  and  back  again.  Whatever  part  of  the  plant  they  infest, 
they  may  live  on  a  single  host  species,  they  may  spread  indefinitely 
from  one  to  several  others,  or  they  may  migrate  definitely,  by 
means  of  a  fixed  generation,  from  one  species  to  another,  requir- 
ing thus  for  their  continuance  two  plant  species  often  extremely 
unlike. 

Finally,  the  sexual,  oviparous  generation  (commonly  the  last 
to  appear  in  fall)  may  leave  its  eggs  on  the  exposed  parts  of  the 
plant  last  infested,  or  it  may  deposit  them  in  the  earth  among  or 
on  the  roots  of  its  host.  In  the  former  case  the  destruction  of  the 
plant,  or  of  its  remains,  will  destroy  the  lice  ;  in  the  latter,  the 
eggs  rest  like  a  seed  in  the  earth  to  stock  the  ground  the  follow- 
ing spring  with  a  horde  of  young,  ready  to  infest  the  succeeding 
crop  if  suited  to  their  tates  and  habits. 

All  the  plant  lice  of  our  present  list  of  species  infesting  the 
roots  of  corn  are,  so  far  as  known,  subterranean  only,  producing 
no  galls,  but  leaving  their  eggs  in  the  earth  over  winter.  They 
infest  more  than  one  plant,  spreading  from  one  to  another  species 
in  an  indefinite  manner,  not  definitely  migrating.  The  corn  and 
grass  root  lice.  (Aphis  maidiradicis  and  Schisoneura  panicola) 

*A  marked  illustration  of  this  fact  is  afforded  by  the  somewhat  recent  history  of  the 
grain  louse  (Sip/wnophora  aveiuz)  in  Illinois.  (See  Seventeenth  Report  State  Ento- 
mologist of  Illinois,  p.  X.) 


l8g6.J        INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  237 


develop  early  in  the  season  winged  forms  by  which  they  easily 
spread  from  field  to  field. 

Six  species  of  plant  lice,  belonging  to  as  many  different  genera, 
have  been  found  by  us  habitually  infesting  corn  roots  in  Illinois. 
By  far  the  most  important  of  these  is  that  commonly  known  as 
the  corn  root  aphis.  This  is,  in  fact,  the  only  one  on  the  list  which 
infests  corn  primarily  as  a  principal  food  plant,  the  others  being 
essentially  species  of  the  meadow  and  pasture,  attacking  corn  but 
lightly,  and  most  commonly  only  when  it  follows  grass. 

The  association  of  all  these  species  with  ants,  which  care  for 
them  in  many  ways,  some  of  them  indispensable,  and  feed  in  turn 
on  excretions  of  their  insect  charges,  is  a  fact  of  special  economic 
significance,  since  the  ant  most  active  in  preserving  the  plant- 
louse  species  must  be  taken  into  account  as  a  factor  in  the  eco- 
nomic problem. 

THE  CORN  ROOT  APHIS. 

{Aphis  maidiradiciSy  Forbes.)  • 
(FiG.  33  —  37.)* 


FlG.  33.  —  Corn  Root  Aphis,  oviparous 
female;  enlarged  fourteen  diameters  : 
a,  hind  tibia,  showing  sensoria. 


FIG.  34. — Male  of  same  species  ;  en- 
larged twenty-five  diameters:  a, 
antenna. 


No  insect  affecting  corn  is  more  deserving  of  the  attention  of 
farmers  and  entomologists  at  the  present  time  than  the  corn  root 
aphis.  It  ranks  as  a  corn  pest  with  the  chinch  bug  and  the  army 

*  A  colored  plate  of  the  oviparous  female,  and  of  winged,  wingless,  and  pupa  forms 
of  the  viviparous  female  of  this  species,  was  published  in  the  Seventeenth  Report  of  the 
Illinois  State  Entomologist. 


238  BULLETIN  NO.  44.  \May, 

worm,  less  injurious  at  any  one  time  than  these  are  locally  and 
occasionally,  but  overtaking  them,  on  the  other  hand,  by  its  gen- 
eral distribution  and  the  constancy  of  its  attack.  Although  it  lives 
upon  the  roots  throughout  the  life  of  the  plant,  the  principal 
damage  is  done  at  the  same  time  as  that  caused  by  wireworms — 
while  the  corn  is  still  small.  It  contrasts  with  the  corn  root  worms 
with  respect  to  the  time  of  its  most  injurious  activity,  the  latter 
coming  in  at  about  the  time  when  the  aphis  generally  begins  to 
loosen  its  hold ;  but  the  two  agree  in  the  fact  that  they  make  their 
first  appearance  in  spring  only  on  ground  which  has  been  in  corn 
for  at  least  a  year  preceding.  The  common  root  worm  is  confined 
throughout  the  season  to  the  field  in  which  it  hatches,  while  the 
aphis  presently  scatters  abroad,  more  or  less  freely  according  to 
the  percentage  of  the  second  and  succeeding  generations  which 
develop  wings.  On  the  other  hand,  although  its  worst  mischief 
coincides  with  that  of  the  wireworms,  it  is  not  commonly  the  case 
that  both  are  especially  injurious  in  the  same  fields,  the  wireworms 
following  grass  of  the  first  and  second  year  preceding,  and  the 
plant  louse  most  commonly  infesting  corn  on  old  corn  ground  only. 
As  lands  recently  in  grass  are  most  likely  to  contain  the  white 
grubs  also,  it  is  not  a  common  thing  to  find  the  corn  root  aphis 
early  in  the  spring  in  grub-infested  fields. 

Its  life  history  is  now  probably  very  well  understood,  but 
thoroughly  effective  remedial  measures,  I  regret  to  say,  are  not 
yet  certainly  known.  Rotation  of  crops  will  often  greatly  decrease 
or  even  prevent  injury  by  dispersing  the  attack,  but  we  have  no 
conclusive  proof  that  this  measure  diminishes  to  any  considerable 
extent  the  number  of  root  lice  in  the  country  during  any  one  year. 
It  is  therefore  probable  that  this  insect  is  increasing  slowly  in 
average  numbers  from  year  to  year,  and  it  may  yet  bring  serious 
disaster  to  agriculture  throughout  the  whole  region  best  adapted 
to  the  culture  of  Indian  corn. 

Although  I  have  no  data  for  a  precise  account  of  its  distribu- 
tion, it  has  been  recognized  by  us  in  all  parts  of  the  State  from 
Cairo  to  the  extreme  northern  limit,  and  has  been  definitely  re- 
ported outside  Illinois,  from  Maryland,  New  Jersey,  Indiana, 
Ohio,  Kentucky,  Minnesota,  and  Nebraska.  It  is  altogether  likely 
that  it  occurs  in  larger  or  smaller  numbers  throughout  the  whole 
corn  belt. 


1896.]        INSECT   INJURIES  To   SEED   AND   ROOT   OF   CORN.  239 


FIG.  35. — Corn  Root  Aphis,  wingless  vi- 
viparous female ;  greatly  enlarged : 
a,  apex  of  abdomen  showing  corni- 
cles, tubercles,  and  cauda. 


FIG.  36. — Pupa  of  same  species  ;  en- 
larged  twenty-one  diameters. 


INJURY   TO   CORN. 

The  corn  root  louse  is  a  suctorial  insect,  taking  only  fluid  food 
through  a  stiff  beak,  which  it  thrusts  into  the  tissues  of  the  plant 
it  feeds  upon,  producing  thus  no  external  injury,  nor,  indeed,  any 
local  internal  effect  discoverable  by  ordinary  methods  of  observa- 
tion. Indications  of  injury  by  this  insect  are  consequently  all  of 
a  general  character,  affecting  the  entire  plant,  and  do  not  materi- 
ally differ  from  those  caused  by  severe  drouth,  except  in  the  fact 
that  they  are  likely  to  be  unequal  in  different  parts  of  the  same 
field  in  a  way  to  indicate  no  connection  with  the  amount  of  re- 
tained moisture  in  the  soil. 

A  noticeably  greater  abundance  in  early  spring  in  the  lower 
parts  of  an  infested  field  seems  to  be  due  to  the  greater  abundance 
there  of  young  weeds  on  which  the  corn  root  aphis  feeds  at  first. 
As  soon  as  the  corn  starts  to  grow  it  may  become  infested,  and 
even  be  killed  outright  before  it  appears  above  ground.  We  have, 
in  fact,  found  the  root  louse  on  the  plant  as  early  as  May  gth,  only 
four  days  after  the  field  was  planted. 

The  dwarfing  of  the  plant,  especially  in  patches  here  and  there, 
with  a  yellowing  or  reddening  of  the  leaves — beginning  of  course 
with  the  lowest  ones — and  a  general  apparent  lack  of  thrift  and  vigor, 
are  sufficient  to  cause  suspicion  of  injury  by  this  louse,  a  suspicion 
which  will  be  confirmed  in  part  if  numerous  burrows  of  ants  are 
seen  in  or  near  the  hills  of  corn.  The  presence  of  ants  in  the  field 
may  be  overlooked  after  the  ground  has  been  recently  cultivated, 


240 


BULLETIN  NO.  44. 


[May, 


but  can  scarcely  escape  attention  shortly  after  a  rain,  when  these 
little  insects  actively  open  up  their  burrows,  heaping  up  the  little 
pellets  of  earth  about  the  openings  of  their  nests. 


FIG.  37. — Winged  viviparous  female  of  Corn  Root  Aphis  ; 
enlarged  sixteen  diameters. 

The  appearances  described  may,  nevertheless,  be  due  either  to 
the  corn  root  blight — a  disease  not  caused  by  insects,  and  hence 
not  treated  in  this  report — or  to  the  grass  root  louse,  a  species 
likewise  attended  by  ants,  but  far  less  injurious  to  corn  than  the 
aphis  under  discussion.  If  the  damage  be  due  to  the  root  blight, 
the  root  lice  themselves  will  be  few  or  wanting ;  and  if  to  the 
grass  louse,  the  fact  may  readily  be  ascertained  by  an  examination 
of  the  roots  of  the  corn. 

The  root  aphis  of  the  corn  is  of  a  bluish  green  color,  slightly 
whitened  by  a  waxy  bloom.  The  form  of  the  body  is  oval,  and 
on  the  hinder  part  of  the  back  are  two  short,  slender,  but  con- 
spicuous, tubes,  standing  erect  or  projecting  slightly  backwards, 
which  may  be  seen  by  the  glass  to  have  open  ends  externally. 
These  are  called  the  cornicles  of  the  aphis,  or,  sometimes,  the 
"honey  tubes,"  it  having  been  formerly  supposed  that  they  were 
the  source  of  the  abundant  excretion  upon  which  the  ant  at- 
tendants of  the  lice  eagerly  feed.  The  grass  louse  (Fig.  40  and  41), 
on  the  other  hand,  is  white  in  color,  with  a  blackish  head  and  other 
blackish  markings,  but  without  any  tint  of  green;  and  it  has  no 
trace  of  cornicles,  their  place  being  taken  by  two  minute  openings 
in  the  corresponding  segment  of  the  body,  each  surrounded  by  a 
delicate  brownish  rim. 

The  evidences  of  serious  injury  by  the  corn  root  aphis  are,  in 
short,  an  unusual  dwarfing  and  discoloration  of  the  corn,  an  abund- 
ance of  small  brown  ants  in  the  field,  nesting  among  the  hills,  and, 
finally,  the  presence  of  the  bluish  green  insects  themselves  upon 
the  larger  roots  of  the  corn,  especially  near  the  base  of  the  stalk. 


1896.]         INSECT  INJURIES   TO   SEED   AND   ROOT   OF   CORN.  241 

The  amount  of  injury  may  vary  from  a  scarcely  noticeable 
check  upon  the  growth  of  the  plant  to  a  total  destruction  of  the 
corn  over  considerable  patches,  up  to  half  an  acre  or  more.  This 
more  serious  effect  is,  however,  rarely,  if  ever,  produced  by  the 
root  louse  alone.  Like  most  insect  enemies, — especially  those  of 
suctorial  habit,  which  abstract  the  sap  of  the  plant  they  feed 
upon, — the  corn  root  aphis  serves  to  intensify  the  effect  of  drouth 
and  other  unfavorable  influences,  and  it  is  often  difficult  to  say 
how  much  is  to  be  ascribed  to  the  action  of  the  insect  pest  and 
how  much  to  other  causes  cooperating. 

There  is  some  evidence  to  the  effect  that  a  too  serious  check 
to  the  growth  of  the  corn  results  in  the  early  evolution  of  a  great 
number  of  winged  plant  lice  of  the  second  spring  generation, 
whose  escape  from  the  fields  in  which  they  start  so  breaks  the 
force  of  the  attack  that  in  a  favorable  season  very  badly  damaged 
plants  may  rally  and  make  good  corn;  but  if  the  insect  injury  is 
followed  or  reinforced  by  drouth,  the  corn  may  grow  sluggishly 
the  whole  season  through,  and  either  fail  to  ear,  or  bear  small 
imperfect  nubbins  only.  Sometimes  a  field  not  infested  the  year 
before  is  permanently  damaged- in  June,  or  even  late  in  May,  as 
the  result  of  an  early  accidental  concentration  of  the  winged  lice 
originating  in  other  fields. 

INJURY   TO   OTHER    PLANTS. 

No  other  crop  plants  are  especially  liable  to  injury  by  this 
aphis,  unless  possibly  we  should  except  broom  corn  and  sorghum. 
Although  not  at  all  uncommon  on  these  plants,  it  does  not  com- 
monly thrive  on  them,  and  so  far  as  my  observations  have  extended, 
can  scarcely  be  called  injurious  to  them.  It  has  been  observed  in 
the  field,  however,  or  bred  in  the  insectary,  on  the  roots  of  a 
number  of  other  species  of  plants,  some  of  which  are,  in  fact, 
important  to  its  maintenance.  Many  of  the  first  generation  hatch 
from  the  egg  in  the  field  before  the  corn  is  ready  to  receive  them, 
and  at  this  time  young  smartweed  plants  and  foxtail-grass  (Polyg- 
onum  and  Setaria)  are  their  principal  resource.  These  plants 
harden  early  and  lose  the  succulence  which  makes  them  especially 
desirable  to  plant  lice,  a  fact  which  accounts  in  part  no  doubt  for 
the  early  transfer  of  the  lice  to  corn;  but  in  fields  of  small  grain, 
Setaria  and  Polygonum  may  continue  to  support  the  corn  root 
louse  at  least  until  the  second  generation  is  well  matured.  Indeed, 
I  have  found  this  insect  on  the  roots  of  smartweed  more  than  a 
foot  high  as  late  as  June  I7th.  Crab-grass  (Panicum)  also  becomes 
infested,  but  less  abundantly  than  the  Setaria,  and  from  the  latter 
part  of  June  throughout  the  rest  of  the  season  the  aphis  breeds 


242  BULLETIN   NO.   44.  [May, 

abundantly  on  the  common  purslane  (Portulaca  oleraced).  We 
have  occasionally  found  it  so  abundant  on  purslane  plants  far 
removed  from  corn  fields — beside  paths  in  lawns  and  in  other 
similar  situations — that  one  might  well  regard  this  as  a  purslane 
aphis,  if  it  were  not  for  the  fact  that  this  weed  starts  too  late  in  the 
season  to  serve  as  food  for  the  earlier  generations. 

We  have,  further,  experimental  evidence  that  the  corn  root 
aphis  can  live  on  roots  of  ragweed  (Ambrosia),  having  transferred 
May  8,  1889,  half-grown  young  of  the  second  generation  from 
smartweed  roots  to  this  plant,  where  they  lived  and  fed  until  they 
acquired  wings,  five  days  later.  The  fall  oviparous  generation  and 
the  one  preceding  it  have  been  repeatedly  reported  by  my  field 
assistants — who  were  constantly  dealing  with  the  root  aphis  and 
knew  its  characters  perfectly — to  have  abundantly  infested  dock 
(Rumex  crispus),  fleabane  (Erigeron  canadense),  mustard  (Brassica 
nigra),  sorrel  (Oxalis  stricta),  plantain  (Plant ago  major),  Hungarian 
grass  (Setaria  germanica),  pigweed  (Amarantus  hybridus),  and 
squash;  but  as  these  statements  were  not  verified  by  successful 
transfers  from  these  various  plants  to  corn,  they  rest  only  on 
determinative  evidence,  notoriously  unreliable  with  respect  to  the 
plant  louse  species.  Indeed,  an  attempt  at  transfers  of  the  sup- 
posed corn  aphis  found  on  squash,  sent  me  from  Ohio  by  Prof. 
C.  M.  Weed,  entirely  failed.  A  similar  result  was  reached  in  an 
attempt  to  transfer  known  corn  root  lice  from  corn  to  wheat  and 
oats,  begun  April  22d,  1889.  Insects  placed  on  roots  of  wheat  in 
breeding-cages  April  22d  continued  to  live  there  until  May  5th,  but 
without  producing  young.  May  nth,  however,  all  had  left  the 
plants.  An  earlier  experiment,  begun  April  loth,  had  a  like  ending, 
and  a  precisely  similar  result  was  obtained  in  a  parallel  experiment 
with  oats. 

The  repugnance  of  this  insect  to  the  roots  of  small  grain  was 
repeatedly  shown  also  by  field  observations.  Fields  of  oats  and 
wheat  on  old  corn  grounds,  sometimes  known  to  have  been  badly 
infested  by  the  root  aphis  the  preceding  year,  ofte'n  contained  in 
April  and  May  large  numbers  of  these  root  lice  and  their  asso- 
ciated ants,  the  former  feeding  on  the  roots  of  smartweed  and 
pigeon-grass  growing  with  the  grain,  but  never  being  seen  on  the 
roots  of  the  grain  even  where  these  and  the  grass  roots  were 
closely  interlaced. 

The  relation  of  this  louse  to  other  plants  than  corn  has  an 
important  economic  bearing.  For  example,  in  fields  on  old  corn 
ground,  the  first  generation  of  plant  lice  are  very  noticeably  more 
abundant  early  in  spring  in  the  lower  parts  of  the  field  than  else- 
where, especially  in  those  parts  so  situated  as  to  receive  the  wash 


1896.]         INSECT  INJURIES   TO   SEED   AND   ROOT   OF   CORN.  243 

from  the  remainder.  I  can  at  present  only  account  for  this 
unquestionable  fact  by  the  very  much  greater  abundance  here  of 
young  smartweed  plants,  doubtless  due  to  the  washing  down  of 
the  seeds  left  on  the  ground  in  fall.  This  seems  especially  likely 
to  be  the  true  explanation,  since  the  difference  in  the  number  of 
plant  lice  on  low  and  high  ground  in  the  same  field  diminishes 
greatly  or  entirely  disappears  with  the  advent  of  later  generations 
and  the  scattering  of  the  winged  lice  abroad. 

LIFE   HISTORY. 

General  Statement. — The  corn  root  aphis  passes  the  winter  as 
an  egg  in  the  earth,  in  corn  fields  or,  rarely,  in  other  grounds 
where  purslane  grows  late  in  fall,  always,  so  far  as  known,  only 
in  the  nests  of  a  small  brown  ant  about  an  eighth  of  an  inch  long, 
known  to  science  as  Lasius  niger  or  its  variety,  L,  niger  alienus, 
This  ant  is  the  constant  companion  of  the  root  louse  throughout 
the  year,  living  in  burrows  among  the  roots  of  the  corn.  The 
aphis  eggs  begin  to  hatch  about  the*  time  of  the  opening  of  the 
seed  leaves  of  the  smartweed  or  heartweed  (Polygonumpersicaria), 
abundant  in  cultivated  ground.  This  first  of  the  spring  generations 
is  readily  distinguished  by  characters  of  form  and  color  from  all 
that  follow.  Appearing  usually  before  the  corn  is  planted,  it  is 
dependent  at  first,  in  our  region,  almost  wholly  upon  the  young 
smartweed  plants.  The  roots  of  these  are  laid  bare  by  the  bur- 
rows of  the  ants,  and  upon  these  roots,  within  their  narrow  tunnels, 
the  lice  will  usually  be  found  thickly  clustered.  Later,  if  the  field 
be  not  planted  to  corn,  our  common  species  of  pigeon-grass 
(Setaria)  divides  the  attention  of  the  lice,  offering  in  fact,  for  a 
little  time,  a  more  succulent  herbage  than  the  rapidly  growing 
smartweed. 

The  second  generation  begins  to  appear  about  the  1st  of  May, 
— we  have  one  breeding-cage  record  of  the  28th  of  April, — and  by 
the  middle  of  that  month  may  be  itself  mature.  Many  of  this 
generation  are  winged,  while  others  are  without  wings,*  the 
winged  form  first  occurring  about  May  loth.t  These  "migrant" 
root  lice  may  live  at  first,  like  those  of  the  preceding  generation, 
upon  smartweed  and  pigeon-grass,  but  more  commonly  they  are 
transferred  to  corn  by  the  little  brown  ant  already  mentioned, 
either  in  the  same  field  or  after  they  have  flown  to  another.  These 
ants  not  only  carry  from  weeds  to  corn  the  root  lice  already  in 

*Two  young  of  this  generation,  born  of  the  same  mother  in  a  glass  tube  enclosing 
a  corn  root,  were  kept  by  us  until  adult,  when  one  proved  to  be  a  wingless  aphis  and 
the  other  winged. 

f  This  generation  is  at  its  best  from  May  I  $th  to  2oth  in  average  years  in  central  Illinois. 


244  BULLETIN  NO.  44.  [May, 

their  possession,  but  burrow  hills  of  corn  in  advance,  eagerly 
seizing  and  conveying  to  their  subterranean  galleries  winged  root 
lice  which  come  their  way. 

The  succeeding  generations  are  not  of  special  economic  inter- 
est with  the  exception  of  the  last  to  occur — the  autumnal,  bi-sexual 
brood,  by  which  the  eggs  are  laid.  Both  males  and  females  of 
this  brood  are  wingless,  and  live  in  the  earth 'like  their  parents, 
occurring  there  from  the  middle  of  September  to  the  middle  of 
November.  The  eggs  which  they  lay  are  taken  in  charge  by  their 
attendant  ants  and  cared  for  during  the  winter. 

Number  of  Generations. — The  eggs  of  the  corn  root  louse  begin 
to  hatch  as  early  as  April  loth,  this  process  continuing,  according  to 
our  observations,  until  May  2d.  Our  numerous  breeding-cage 
experiments,  Although  not  one  of  them  is  continuous  throughout 
the  year,  enable  me  nevertheless  to  give  a  fairly  full  account  of 
the  number  and  succession  of  generations.  According  to  these 
the  first  three  generations  have  an  average  life  of  nineteen  days, 
while  the  fourth  to  the  twelfth  follow  each  other  at  an  average 
interval  of  about  eleven  days*.  Many  of  our  observations  show  that 
a  much  earlier  start  and  a  more  rapid  growth  are  common,  and 
that  a  greater  number  of  generations  may  consequently  occur. 

No  special  attempt  was  made  to  determine  the  number  of 
individuals  a  single  female  may  produce  or  the  relative  produc- 
tiveness of  the  various  successive  generations.  The  fact  is  however 
worthy  of  record  that  a  single  stem  mother  placed  on  a  corn  root 
in  a  breeding  cage  May  4th,  brought  forth  her  first  young  May  6th 
and  her  twelfth  and  last  May  I5th.  At  this  time  the  first-born  was 
a  pupa,  acquiring  wings  on  the  iQth.  The  stem  mother  lived  until 
the  22d,  and  was  then  placed  in  alcohol.  Another  female  of  a 
midsummer  brood  brought  forth  fifteen  young. 

According  to  the  results  of  experiments  conducted  for  the 
purpose  of  determining  the  number  of  moults  of  the  corn  root 
aphis,  and  the  intervals  between  successive  moults,  we  find  that 
this  species  moults  four  times,  at  average  intervals  of  three  or  four 
days.  Our  most  successful  observations  upon  this  and  several 
other  nice  points  of  individual  life  history  were  made  on  isolated 
specimens,  each  placed  upon  the  root  of  a  potted  plant  which  was 
then  passed  through  a  small  glass  tube  and  covered  with  earth  ex- 
cept where  the  tube  enclosed  it.  To  prevent  the  escape  of  the 
plant  louse  the  ends  of  the  tube  were  lightly  plugged  with  cotton- 
wool. 

Migration  to  Uninfested  Fields. — The  last  autumnal  brood  of 
the  corn  root  aphis  lives,  so  far  as  known,  only  upon  roots  of  corn 
and  purslane,  the  latter  being  usually  infested  in  corn  fields  only, 


1896.]        INSECT  INJURIES  TO  SEED  AND   ROOT  OF  CORN.  245 

and  in  these  situations,  consequently,  the  eggs  are  left  from  which 
young  hatch  the  following  spring.*  This  first  spring  generation 
being  always  without  wings,  the  root  aphis  is  practically  confined 
for  a  little  time  to  fields  previously  in  corn.  As  a  considerable 
part  of  the  second  generation  acquires  wings,  a  general  dispersal 
of  adults  begins  almost  as  soon  as  the  corn  is  out  of  the  ground. 
.These  winged  root  lice  do  not,  however,  become  sufficiently 
abundant  for  a  considerable  time  thereafter  to  noticeably  affect 
fields  not  in  corn  the  year  before.  Previous  to  the  first  of  June 
this  distributed  attack  can  scarcely  be  detected,  and  not  until  July 
ist  have  we  found  it  really  serious  anywhere. 

The  evolution  of  winged  root  lice  is  not  confined  to  any  single 
generation,  but  continues  throughout  the  season  in  numbers  vary- 
ing according  to  some  law  not  yet  ascertained.  It  is  to  be  noticed, 
however,  that  we  have  taken  the  winged  form  in  August  but  once, 
although  our  collections  of  wingless  specimens  were  made  on 
twenty-seven  days  within  that  month.  In  September  also  the 
winged  louse  is  relatively  rare,  occurring  but  three  times  in  twenty 
collections  made  on  as  many  different  dates.  By  November  the 
viviparous  generations  are  all  dead,  as  a  rule,  and  the  species  is 
thereafter  represented  only  by  the  sexual  generation  and  the  egg. 

RELATION   TO   ANTS. 

Seven  kinds  of  ants  have  been  found  by  us  fulfilling  the  rela- 
tion of  host,  guardian,  and  nurse  to  the  corn  root  aphis.  The  oc- 
currence in  this  relation  of  all  but  two  (Lasius  niger  and  Lasius 
niger  alienus,  Fig.  38  and  39)  is  so  rare  that  they  need  receive  here 
no  more  than  this  passing  mention,  especially  as  their  services  to 
the  aphis  are,  so  far  as  observed,  the  same  in  character  and  value 
as  those  of  the  much  more  abundant  species. 

The  fact  has  already  been  mentioned  in  this  paper  that  the 
sexual  egg-laying  generation  of  the  corn  root  aphis — the  last  to 
appear  in  fall — is  born  in  the  galleries  of  the  nests  or  homes  of 
ants,  and  that  here  the  sexes  pair  and  the  females  drop  their  eggs. 
As  one  explores  these  nests  in  November,  when  the  root  louse 
eggs  are  being  laid,  he  is  struck  with  the  relative  independence  of 
these  oviparous  adults,  which  are  allowed  to  wander  unattended 
through  the  burrows  of  their  hosts  as  far  as  a  foot  or  more  from  a 
corn  root.  We  have  found  them,  however,  still  feeding  as  late  as 
November  5th,  and  laying  eggs  November  2ist.  These  eggs,  which 
are  yellow  when  first  deposited,  but  soon  become  shining  black, 

*Among  more  than  fifty  lots  of  "  stem  mothers  "  of  the  corn  root  aphis  collected 
by  us  in  the  field,  every  one  was  found  in  ground  which  had  borne  corn  for  at  least  the 
year  immediately  preceding. 


246  BULLETIN  NO.  44.  [May, 

and  turn  green  just  before  hatching,  are  at  first  scattered  here  and 
there,  as  it  happens,  but  are  finally  gathered  by  the  ants  for  the 
winter  in  little  heaps  and  stored  in  their  galleries,  or  sometimes  in 
chambers  made  by  widening  the  gallery  as  if  for  storage  purposes. 
If  a  nest  is  disturbed,  the  ants  will  commonly  seize  the  aphis  eggs 
— often  several  at  a  grasp — and  carry  them  away.  In  winter  they 
are  taken  to  the  deepest  parts  of  the  nests  (six  or  seven  inches  be-, 
low  the  surface  in  some  cases  observed)  as  if  for  some  partial  pro- 
tection against  frost;  but  on  bright  days  in  spring  they  are 
brought  up,  sometimes  within  half  an  inch  or  less  of  the  surface, 
sometimes  even  scattered  about  in  the  sunshine,  and  carried  back 
again  at  night — a  practice  probably  to  be  understood  as  a  means  of 
hastening  their  hatching.  I  have  repeatedly  seen  these  ants  in 
confinement  with  a  little  mass  of  aphis  eggs,  turn  the  eggs  about 
one  by  one  with  their  mandibles,  licking  each  carefully  at  the  same 
time  as  if  to  clean  the  surface.  These  anxious  cares  are  of  course 
explained  by  the  use  the  ants  make  of  the  root  lice,  whose  ex- 
creted fluids  they  lap  up  greedily  as  soon  as  the  young  lice  begin 
to  feed.  They  are  not,  however,  wholly  dependent  on  this  food 
supply,  at  least  in  early  spring,  as  I  have  seen  them  kill  and 
drag  away  at  that  season  soft-bodied  insect  larvae,  doubtless  to 
suck  their  juices  out  as  food.  This  has  been  a  somewhat  rare  oc- 
currence, however,  and  has  rarely  been  noticed  by  us  among  ants 
which  had  plant  lice  in  their  possession.  Once,  however,  ants  of 
this  species  occurring  abundantly  in  corn  fields  were  observed 
September  22d  to  carry  bits  of  dead  insects  into  their  burrows,  to- 
gether with  a  living  corn  root  louse. 

That  the  young  of  the  first  generation  are  helped  by  the  ants 
to  a  favorable  position  on  the  roots  of  the  plants  they  infest  is 
quite  beyond  question.  It  is  shown  (i)  by  the  fact  that  in  many 
cases  the  aphis  could  not  get  access  to  such  roots  unless  these  had 
been  previously  laid  bare  by  the  tunneling  of  the  ants,  and  (2)  by 
the  behavior  of  ants  with  mines  already  constructed,  when  the 
root  aphis  is  offered  to  them.  We  have  repeatedly  performed  the 
experiment  of  starting  colonies  of  ants  on  hills  of  corn  in  the 
insectary  and  exposing  root  lice  from  the  field  to  their  attentions, 
and  in  every  such  instance,  if  the  colony  was  well  established,  the 
helpless  insects  have  been  seized  by  the  ants,  often  almost  instantly, 
and  conveyed  under  ground,  where  we  would  later  find  them  feed- 
ing and  breeding  on  the  roots  of  the  corn.  In  many  cases  in  the 
field,  we  have  found  the  young  root  aphis  on  sprouting  weeds 
(especially  pigeon-grass),  which  have  been  sought  out  by  the  ants 
before  the  leaves  had  shown  above  the  ground;  and,  similarly, 
when  the  field  is  planted  to  corn,  these  ardent  explorers  will 


1896.]        INSECT  INJURIES  TO  SEED  AND  ROUT  OF  CORN.  247 

frequently  discover  the  sprouting  kernel  in  the  earth,  and  mine 
along  the  starting  stem  and  place  the  plant  lice  upon  it. 

We  have  also  abundant  evidence  that  ants  excavate  hills  of 
corn  in  very  early  spring,  when  they  have  as  yet  neither  eggs  nor 
plant  lice  in  their  possession,  and  some  days  before  the  possible 
appearance  of  the  second  or  winged  generation.  I  can  only  account 
for  this  practice  on  the  supposition  that  these  ants  expect  later  to 
obtain  eggs  or  young  with  which  to  stock  their  burrows,  made 
ready  in  advance.  Certainly  this  is  true  with  respect  to  the  second 
generation  of  the  root  aphis.  When  winged  lice  of  this  brood 
begin  to  appear,  it  is  a  common  thing  to  find  the  small  brown  ant 
scattering  far  and  wide  over  fields  not  previously  in  corn,  and  con- 
taining consequently  no  plant  lice  in  any  stage,  burrowing  there 
the  hills  of  corn,  and  carrying  underground  such  corn  root  lice  as 
come  within  their  range. 

I  need  hardly  say  that  the  relations  above  described  between 
the  corn  root  aphis  and  these  ants  continue  without  cessation 
throughout  the  year,  the  succeeding  generations  being  quite  as 
useful  to  the  ants  as  those  whose  history  I  have  thought  it  worth 
while  to  follow  in  detail. 

NATURAL   ENEMIES. 

Although  various  insect  species,  mites,  ground  beetles,  and 
the  like,  have  been  found  in  more  or  less  suspicious  relation  to  the 
corn  root  lice  in  our  breeding-cages,  and  even  in  the  fields,  no 
known  case  has  occurred  with  us  of  destruction  by  an  insect  enemy. 
It  is,  indeed,  a  remarkable  fact  that  not  a  single  hymenopterous 
parasite  has  ever  been  bred  from  the  corn  root  aphis  in  all  our 
long  experience  with  that  insect.  It  is  true  that  root  lice  are  much 
less  parasitized  than  those  feeding  in  more  exposed  positions,  but 
they  are  nevertheless  by  no  means  commonly  free  from  parasitic 
attack. 

The  only  natural  check  upon  the  increase  of  this  root  aphis 
which  has  come  immediately  to  our  notice  is  a  parasitic  fungus, 
Entomophthorafresenii,  detected  October  16,  1889,  infesting  sexual 
individuals  of  this  species  found  on  roots  of  the  curled  dock 
(Rumex  crispus}  at  Champaign,  Illinois.  Affected  specimens  were 
of  a  creamy  or  whitish  color,  and  were  literally  crammed  with  the 
small  oval  granular  spores  of  the  Entomophthora. 

ECONOMIC   PROCEDURE. 

Our  present  knowledge  of  the  life  history  of  the  corn  plant 
louse  suggests  four  possible  methods  of  attack,  (i.)  We  may 


248  BULLETIN  NO.  44.  \May> 

try  the  effect  of  a  change  of  crop  after  any  notable  plant-louse 
injury  to  corn,  in  the  expectation  that  corn  planted  on  ground 
which  contains  no  plant-louse  eggs  will  become  so  slightly  or  so 
slowly  infested,  if  at  all,  that  no  harm  need  be  anticipated.  (2.) 
We  may  resort  to  fertilizers  and  other  applications  made  to  the 
young  corn  hill  in  spring  in  the  hope  of  killing  the  lice  outright 
or  of  supporting  the  plant  against  their  attack  at  a  time  when  this 
is  likely  to  be  most  injurious.  (3.)  Since  the  small  brown  ant 
cares  assiduously  for  the  eggs  in  winter  and  spring,  we  may 
assume  provisionally  the  necessity  of  such  care  and  strive  to  find 
means  of  so  disturbing  the  nests  of  the  ants  or  of  breaking  up  and 
dispersing  their  contents  in  late  fall  or  in  winter  that  their  stores 
of  aphis  eggs  cannot  be  recovered  by  them,  and  so  shall  be  left 
to  perish.  (4.)  Taking  account  of  the  early  hatching  of  the  eggs 
in  spring — several  days,  as  a  rule,  before  the  usual  time  for  plant- 
ing corn, — and  the  dependence  of  the  young  lice  for  food  at  that 
time  on  sprouting  weeds  in  the  field, — especially  smartweed  and 
pigeon-grass, — we  may  seek  to  handle  the  ground  in  such  a  man- 
ner that  there  shall  be  no  sufficient  start  of  vegetation  to  keep  the 
lice  alive.  We  may  also  delay  somewhat,  if  necessary  to  this  end, 
the  planting  of  the  field  to  corn. 

Rotation  of  Crops. — There  can  be  no  doubt  that  a  judicious 
rotation  of  crops  has  the  effect  at  least  to  diminish  injury  by  the 
corn  plant  louse  by  distributing  its  attack ;  and  there  is  also  con- 
siderable reason  to  believe  that  it  must  result  in  the  destruction, 
direct  or  indirect,  of  a  certain  proportion  of  the  insects  themselves. 
Corn  planted  on  ground  not  previously  stocked  with  plant-louse 
eggs  must  escape  at  any  rate  until  invaded  from  without  by  winged 
individuals  of  the  second  generation,  and  then,  as  a  rule,  it  will  be 
no  more  subject  to  injury  than  the  other  fields  in  its  neighborhood. 
On  the  other  hand,  as  the  corn  root  aphis  has  never  been  known 
to  infest  to  an  injurious  extent  any  other  crop  following  corn, 
there  is  very  little  probability  that  the  escape  of  the  corn  will  be 
balanced  by  damage  to  other  crops. 

We  have  many  observations  going  to  show  that  wheat  and 
oats  and  the  smaller  grass-like  plants  in  general  are  commonly 
soon  deserted  by  such  corn  root  lice  as  commence  to  breed  on 
them — a  fact  which  indicates  that  these  plants  are  less  suitable 
than  corn  to  the  maintenance  and  multiplication  of  these  insects. 
We  have  also  considerable  reason  to  believe  that  many  winged 
plant  lice  flying  about  in  search  of  feeding  and  breeding  grounds 
must  be  destroyed  by  some  of  the  innumerable  accidents  to  which 
these  feeble  and  helpless  insects  are  necessarily  exposed.  This 
measure  of  rotation  may  consequently  have  the  effect  to  diminish 


1896.]        INSECT  INJURIES  TO  SEED  AND  ROOT  OF  CORN.  249 

to  an  important  extent  the  number  of  corn  root  lice  in  later  gen- 
erations. Precise  proof  on  these  points  is,  however,  very  difficult 
to  secure.  Artificial  breeding  experiments  are  altogether  too 
variable  in  result  to  serve  the  purpose,  as  our  own  attempts  at  a 
solution  of  this  question  show;  and  evidence  must  be  sought  in  the 
field  especially  by  making  detailed  comparative  observations  of 
parts  of  the  same  previously  infested  fields,  planted  here  to  corn 
and  there  to  small  grain.  The  relative  abundance  of  the  lice  late 
in  May  and  early  in  June  will  go  far  to  show  the  comparative 
utility  of  these  crops  as  a  food  resource  to  the  corn  root  aphis. 

Applications  of  Fertilizers  and  Insecticides. — Various  field  obser- 
vations have  given  us  reason  to  conclude  that  fertilization  of  the 
soil  will  serve  to  support  corn  under  the  drain  of  aphis  injury, 
especially  by  enabling  a  stunted  plant  to  rally  more  rapidly  and 
completely  after  the  insects  have  begun  to  scatter.  The  rapidity 
and  vigor  with  which,  in  rich  ground  and  in  a  fairly  favorable 
season,  corn  will  outgrow  an  apparently  fatal  injury  by  the  root 
aphis  is,  in  fact,  often  quite  surprising.  Apart  from  this  general 
statement  I  have  only  to  report  the  result  of  a  single  series  of  plat 
experiments  tried  in  1891  with  various  fertilizers  mingled  with 
petroleum,  crude  and  refined,  as  an  insecticide,  and  with  applica- 
tions of  salt,  wood  ashes,  and  lime. 

A  plat  of  ground  ten  hills  square,  containing  ninety-seven 
hills  of  corn,  was  selected  on  the  University  experimental  farm  at 
Urbana  June  18,  1891,  and  surround-ed  by  a  continuous  line  of  six- 
inch  boards  sunk  about  three  inches  into  the  ground,  with  close- 
fitting  joints,  and  with  the  earth  well  tramped  both  outside  and  in. 
The  upper  edge  of  the  boards  was  thickly  covered  with  coal-tar, 
subsequently  kept  fresh  by  repeated  applications.  These  meas- 
ures were  intended  to  prevent  all  interference  with  the  experi- 
ment, either  by  escape  of  the  insects  within  the  plot  or  by  invasion 
from  without.  June  26th  this  enclosure  was  enlarged  to  contain 
twenty-three  hills  more.  Fertilizers,  and  mixtures  of  fertilizers 
and  petroleum,  were  applied  to  the  hills  of  corn  June  i8th  and  23d, 
being  worked  into  the  soil  about  each  hill;  and  on  the  26th  lime, 
ashes,  and  salt  were  similarly  applied.  Of  the  ninety-seven  hills 
in  the  first  enclosure,  forty-eight  were  found  in  the  beginning  to 
contain  root  lice  and  ants,  and  of  the  twenty-three  hills  in  the 
second  lot  sixteen  were  similarly  infested. 

Three  fertilizers  were  applied :  superphosphates,  muriate  of 
potash,  and  sulphate  of  potash,  each  at  the  rate  of  three  pounds  to 
twenty  hills  of  corn,  and  in  each  case  half  the  hills  under  experi- 
ment were  treated  with  the  pure  fertilizer  and  the  other  half  with 
a  mixture  of  fifteen  ounces  of  petroleum  to  three  pounds.  One- 


250 


BULLETIN  NO.  44. 


\May, 


third  of  the  above  amounts  were  applied  June  i8th, — the  petroleum 
in  these  cases  being  the  crude  Lima  oil, — and  the  remaining  two- 
thirds,  June  23d,  when  refined  petroleum  was  used.  The  following 
notes  are  condensed  from  the  memorandum  filed  at  the  time  by 
the  assistant*  in  charge  of  the  experiment: 

Experiment  I.,  Superphosphates.     Experiment  II.,  Superphosphates  and  Petroleum. 

June  29,    I.  Ants  and  root  lice  numerous. 

"  29,  II.  Both  insects  present  but  less  numerous  than  in  I. 

July  i,    I.  Ants  and  lice  abundant. 

"  I,  II.  Ants  present  but  no  lice. 

"  7,  .1.  Ants  and  lice  abundant. 

"  7,  II.  A  few  ants  but  no  lice. 

"  15,    I.  Ants  and  lice  comparatively  abundant. 

"  15,  II.  Ants  and  lice  both  present  but  fewer  than  in  I. 


Experiment  III.,    Muriate   of  Potash. 
Petroleum. 


Experiment    IV.,    Muriate   of   Potash  and 


June  29,    III.     A  few  ants  and  lice  found. 

"      29,     IV.     Dead  plant  lice  discovered  in  one  hill,  both  ants  and  lice  occur- 
ring generally  but  not  abundantly. 
July     I,    III.     A  few  ants  but  no  lice. 
"        i,    IV.     Ants  alone  discovered  on  roots  about  one  foot  from  the  hill,  just 

outside  the  fertilized  area. 
7,    TIL     Ants  and  root  lice  found. 
"        7,    IV.     Ants  but  no  lice. 
"      15,    III.     Ants  plentiful ;  lice  common. 
"      15,    IV.     Few  ants  and  lice  detected. 


Experiment   V.,    Sulphate  of  Potash. 
Petroleum. 


Experiment  VI.,  Sulphate  of  Potash  and 


June  29,  V.  Ants  present  but  no  lice. 

"  29,  VI.  A  few  ants  present  but  no  lice. 

July  i,  V.  Neither  ants  nor  lice  were  found. 

"  i,  VI.  A  few  ants  and  lice  in  one  hill. 

"  7,  V.  Ants  and  lice  numerous. 

"  7,  VI.  Both  insects  present. 

"  15,  V.  No  ants  or  lice  detected. 

"  15,  VL  Small  colony  of  ants  and  a  few  lice  in  one  hill. 

The  weather  during  the  period  covered  by  the  above  experi- 
ment was  generally  dry,  but  abundant  rains  occurred  June  20th  and 
2ist,  which  seemed  to  dissolve  the  fertilizers  and  wash  them  into 
the  ground. 

The  lime,  ashes,  and  salt  experiments  were  entirely  without 
effect,  ants  and  plant  lice  occurring  abundantly  in  all  parts  of  the 
plat  treated  throughout  the  entire  period  of  observation  to  July 
28th.  This  plat  served  consequently  as  a  check  upon  the  preced- 
ing experiment. 

Although  the  effect  of  the  other  applications  seems  from  the 
above  notice  to  be  quite  marked,  the  experiment  is  nevertheless 
indecisive,  since  the  hills  treated  were  not  dug  up  when  examined 
from  time  to  time,  but  only  searched  as  carefully  as  was  possible 

*Mr.  J.  S.  Terrill.     The  work  was,  however,  done  under  the  immediate  supervision 
of  Mr.  John  Marten,  one  of  my  present  entomological  assistants. 


1896.]        INSECT  INJURIES  TO  SEED  AND   ROOT   OF  CORN.  2$I 

without  injuring  the  plants.  July  28th,  when  all  the  hills  were  re- 
moved, they  seemed,  according  to  Mr.  Marten's  report,  to  be  about 
equally  infested,  all  appearance  of  difference  having  then  vanished. 
It  will  thus  be  seen  that  these  experiments  have  little  value 
except  as  hints  towards  future  work.  The  differences  observed 
may  nearly  all  have  been  due  to  a  repellent  effect  of  the  sub- 
stances applied,  in  consequence  of  which  the  ants  withdrew  their 
charges  deeper  into  the  earth,  with  little  diminution  perhaps  of 
the  injury  to  the  corn. 

Breaking  iip  Nests  of  Ants. — In  one  experiment,  begun  Novem- 
ber 25,  1890,  a  strip  of  corn  stubble  three  rods  wide  and  ten  rods 
long  near  the  University  premises  at  Champaign,  was  plowed  six 
inches  deep,  half  the  strip  being  thoroughly  harrowed  also.  The 
ants'  nests  among  the  corn  hills  were  thus  turned  out  and  thor- 
oughly broken  up,  except  that  in  a  few  cases  the  plow  did  not  go 
the  full  depth  of  the  nests,  but  left  the  bottom  undisturbed.  The 
harrowing  knocked  the  dirt  out  of  the  roots  of  the  corn  and  broke 
up  the  fragments  of  the  nests  remaining  in  the  clods.  April  18, 
1891,  when  the  ground  was  again  plowed,  five  ants'  nests  were 
found  in  this  plat  and  thirteen  in  an  equal  strip  beside  it.  All  of 
these  outside  nests  contained  ant  larvae  of  various  sizes,  while 
those  inside  the  strip  contained  no  ants  but  worker  adults.  Ten 
of  the  former  lot  of  nests  and  three  of  the  latter  contained  root 
lice  also,  on  smartweed  roots. 

In  another  precisely  similar  experiment,  begun  upon  the 
same  day  in  an  adjoining  field,  a  strip  was  plowed  two  and  a  half 
rods  wide  by  twelve  rods  long,  half  of  this  being  thoroughly  har- 
rowed, as  before.  The  plowing  averaged  six  inches  in  depth, 
but  the  plow  ran  considerably  deeper  under  the  corn  rows,  and 
the  ants'  nests  were  well  broken  up  and  scattered.  April  i/th  of 
the  following  spring  the  ground  was  plowed  for  corn  and  thor- 
oughly examined  to  determine  the  result  of  the  experiment.  The 
part  which  was  harrowed  contained  three  ants'  nests,  the  remain- 
der six ;  while  on  an  equal  strip  adjoining,  thirty  were  found. 
None  in  the  strip  plowed  in  fall  contained  young  ants,  while 
every  one  of  those  outside  contained  them.  Several  wingless 
females  were  seen  in  the  nests,  one  of  them  in  the  plowed  strip. 

Neither  the  weather  at  the  time  nor  that  of  the  following 
winter  was  especially  favorable  to  the  success  of  such  an  experi- 
ment, the  mercury  reaching  a  maximum  of  49°  F.  on  the  day  the 
experiment  began,  and  the  winter  following — that  of  1890-91 — 
being  unusually  open  and  warm.  Further,  there  had  been  more 
than  a  week  of  warm  spring  weather  previous  to  April  i8th,  the 
mercury  reaching  72°  on  the  gth,  75°  on  the  I3th,  and  77°  and  78° 


252  BULLETIN  NO.  44.  [May, 

on  the  1 7th  and  i8th  respectively — temperatures  at  which  ants  as 
active  as  the  little  Lasius  niger  alienus  might  well  disperse  them- 
selves and  begin  new  colonies  in  unoccupied  ground. 

These  experiments  afford,  perhaps,  scarcely  a  sufficient  basis 
for  a  final  conclusion  as  to  the  economic  value  of  this  method,  but 
so  far  as  they  go  they  are  most  encouraging.  If  we  compare  the 
treated  plats  with  the  check  plats  beside  them,  we  find  (i)  that  the 
ants'  nests  in  the  former  were  less  than  a  third  as  many  as  in  the 
latter;  (2)  that  all  in  the  plowed  and  harrowed  plats  were  destitute 
of  ant  larvae  while  in  the  check  plats  all  without  exception  con- 
tained such  larvae;  and  (3)  that  in  the  single  plat  first  mentioned 
the  ants'  nests  containing  lice  were  less  than  a  third  as  numerous 
as  those  in  the  plat  outside.* 

From  the  above  we  can  only  infer  the  disastrous  effect  of  this 
late  fall  and  winter  plowing  upon  the  ants  themselves,  and,  pre- 
sumably, also  upon  the  plant  louse  eggs  they  have  in  charge.  It 
seems  also  quite  probable  that  some,  if  not  all,  of  the  nests  found 
April  i8th  in  the  experimental  plats  had  been  established  there  by 
worker  ants  in  spring,  and  were  not  remnants  of  the  nests  previ- 
ously broken  up,  and  if  this  were  the  case  the  root  lice  found  in 
them  had  doubtless  been  brought  in  from  without. 

Starvation  Experiments, — April  15,  1889,  twelve  young  root 
lice  recently  hatched  were  placed  in  a  cavity  in  the  moist  earth, 
which  was  covered  with  a  glass  slip  so  placed  as  to  allow  an  exami- 
nation of  the  interior.  April  2Oth  two  of  these  root  lice  died;  the 
next  day  half  the  lot  were  dead;  April  22d  only  two  were  living; 
April  23d  but  one;  and  on  April  24th,  nine  days  from  the  beginning 
of  the  experiment,  all  were  dead. 

May  14,  1888,  a  number  of  corn  root  lice  of  various  ages,  taken 
from  the  roots  of  young  smartweed  in  the  field,  were  placed  in  a 
glass  vial  with  moist  earth,  the  mouth  of  the  vial  being  covered 
with  gauze.  On  the  i8th  all  were  still  alive,  but  by  the  20th  all 
had  died,  the  earth  in  the  vial  still  remaining  moist. 

April  30,  1890,  a  number  of  eggs  were  placed  in  a  cavity  in 
sterilized  earth  and  left  to  themselves.  May  ist  one  young  louse 
appeared  from  the  only  egg  of  the  lot  which  hatched,  and  May  3d 
this  one  was  dead.  It  appeared  from  the  foregoing  that  young  of 
this  species  hatching  in  the  earth  and  kept  without  food  would  die 
in  from  two  to  nine  days. 

As  a  field  application  of  this  fact,  an  attempt  was  made  April 
16,  1889,  to  starve  the  young  lice  in  the  ground  by  keeping  down 
the  growth  of  young  weeds.  A  piece  of  ground  was  thoroughly 

*By  an  unfortunate  oversight  no  mention  was  made  in  the  notes  on  the  second 
experiment,  of  root  lice  in  either  the  plowed  strip  or  check. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  253 

harrowed  in  two  directions  with  a  cutaway  disk  harrow,  and  the 
weedier  parts  of  the  plot,  several  times  additional.  April  20th,  how- 
ever, ants  and  lice  were  found  both  within  and  without  the  har- 
rowed strip;  but  the  ants  had  no  plant-louse  eggs  in  their 
possession  where  the  ground  had  been  harrowed.  The  result  of 
this  treatment  was  not  especially  encouraging,  the  young  weeds 
sprouting  so  freely  and  abundantly  in  the  moist  earth,  to  a  depth 
of  four  or  five  inches,  that  it  seemed  impossible  to  reduce  the  food 
supply  of  the  lice  to  any  considerable  extent  by  mechanical 
methods. 

Our  present  knowledge  of  effective  economic  procedure  for 
the  corn  root  aphis  may  be  summarized  in  the  form  of  the  follow- 
ing recommendations:  (i)  that  the  fertility  of  the  ground  should 
be  maintained  as  a  general  safeguard,  and  that  cultivation  should 
be  so  managed — especially  that  of  the  lower  parts  of  the  field — as 
to  prevent  so  far  as  practicable  the  seeding  of  pigeon-grass  and 
smartweed  among  the  corn;  (2)  that  infested  fields  should  be 
plowed  deeply  and  thoroughly  harrowed  late  in  fall  or  during 
some  suitable  early  winter  interval;  and  (3)  that  a  somewhat 
rapid  rotation  of  crops  should  be  systematically  followed,  corn 
usually  being  allowed  to  grow  on  the  same  ground  but  two  years 
in  succession.  While  some  work  remains  to  be  done  with  refer- 
ence to  the  precise  value  of  these  methods  in  practical  application, 
there  is  no  longer  any  doubt  of  their  substantial  usefulness,  at 
least  as  a  means  of  holding  in  check  the  injuries  of  the  corn  root 
aphis. 

ON  THE  ANTS  ATTENDANT  UPON  THE  CORN  ROOT  APHIS. 


FIG.   38. — Small   Brown   Ant   (Lasius  niger  alienui),  female ;  enlarged 
four  and  a  half  diameters. 

Lasius  niger  and  its  variety  aliemts  are  so  far  the  most  abund- 
ant of  the  seven  species  of  ants  which  we  have  found  in  attend- 
ance upon  the  corn  root  aphis  that  a  discussion  of  the  economics 


254  BULLETIN  NO.  44.  [May, 

of  this  relation  need  scarcely  take  account  of  any  other  species ; 
but  as  the  most  promising  protective  measures  against  this  aphis 
are  based  on  our  knowledge  of  the  life  history  and  habits  of  this 
commonest  corn-field  ant,  an  accurate  account  of  the  latter  is  to 
be  desired.  Our  notes  on  this  subject  cover  the  entire  period 
since  1883,  and  enable  me  to  give  a  fairly  complete  history  of  this 
species  throughout  the  year. 

Life  History. — The  winged  sexual  forms,  male  and  female,  of 
this  ant  begin  to  appear  each  year  as  early  as  the  latter  part  of 
June  (the  2ist  to  the  27th),  hatching  from  pupae  which  may  have 
formed  late  in  May  (27th  and  28th,  by  our  notes).  The  emergence  of 
males  and  females  from  the  pupa  continues  throughout  the  season, 
certainly  into  October  and  probably  to  November,  but  the  males 
perish  before  the  winter.  The  females,  however,  having  been  fer- 
tilized and  deprived  of  their  wings,  begin  their  separate  excava- 
tions in  fall,  or  continue  with  the  workers  in  nests  already  estab- 
lished. There  they  hibernate,  sometimes  at  least,  commencing  to 
lay  their  eggs  in  fall,  and  living  in  spring  through  April  and  May. 
We  have  found  the  eggs  of  this  species  only  November  loth, 
April  25th,  and  May  20th;  but  exceedingly  small  larvae  certainly  very 
recently  hatched  have  been  collected  by  us  May  5th  to  iQth,  July 
I5th,  and  September  2ist.  Our  experiments  have  not,  however, 
been  conducted  in  a  way  to  distinguish  between  eggs  and  young 
coming  from  fully  developed  females  and  those  from  fertile  workers. 
The  larvae  hatching  from  time  to  time  throughout  the  summer 
may  be  found  as  pupae  from  the  latter  part  of  May  through  June, 
July,  August,  and  September,  to  October  3Oth,  and  even,  according 
to  a  single  observation  made  at  Urbana,  to  November  2Oth. 

Haunts,  Actions,  and  Habits. — The  nests  or   burrows  of  this 
ant,  in  which  these  breeding  operations  are  carried  forward,  are 

widely  distributed  in  corn  fields  and 
grass  lands, — especially  in  the  latter, 
along  the  borders  of  roads  and  paths, 
— and  also  under  stones  and  boards, 
in  and  under  decaying  logs,  and  in  an 
indefinite  variety  of  situations.  In 
corn  fields  they  are  established  almost 
wholly  in  the  hills  of  corn,  and  remain 
here  among  the  old  corn  roots 
throughout  the  season.  As  this  is  the 
commonest  and  most  generally  dis- 
tributed of  all  our  ants  in  Illinois,  an 
exhaustive  list  of  its  places  of  habita- 

tion  would  have  little  Present  interest- 

fourth  diameters,  Jt  has  never  been  found  by  us  to  form 


1896.]        INSECT  INJURIES  TO   SEED  AND   ROOT  OF  CORN.  255 

large  settlements,  or  making  mounds  or  conspicuous  structures  of 
any  kind;  but  simply  scatters  its  little  burrows  almost  indiscrim- 
inately, living  in  small  families  rather  than  in  great  colonies  or 
city-like  aggregations,  and  piling  up  only  a  small  temporary  heap 
of  pellets  around  the  mouth  of  its  burrow.  When  its  mines  are 
explored  they  are  found  to  consist  of  irregularly  radiating  and  con- 
nected tunnels,  rarely  going  to  a  greater  depth  than  six  or  eight 
inches,  or  extending  outward  over  a  horizontal  area  of  more  than 
twelve  or  fifteen  inches.  Here  and  there  in  their  course  or  at 
their  extremities  and  at  various  depths  are  chamber-like  enlarge- 
ments in  which  their  eggs  and  young  and  the  eggs  of  the  corn  root 
aphis  are  preserved  and  cared  for.  Here  also  considerable  collec- 
tions of  the  worker  ants  are  usually  found, — especially  in  winter, 
and  in  times  of  summer  drouth, — and  in  these  chambers  the  fe- 
male resides  and  lays  her  eggs. 

In  April,  May,  and  June  the  workers  seem  to  be  most  num- 
erous and  active.  In  July  and  August  their  activity  declines, 
particularly  in  the  hottest  and  dryest  weather,  although  if  nests 
be  opened  at  these  times  the  ants  will  be  found  in  abundance. 
Again,  in  September,  a  period  of  bustling  activity  begins  which 
continues  until  checked  by  the  winter  cold. 

In  ordinary  winter  weather  of  the  milder  sort,  these  ants  are 
not  absolutely  motionless,  but  if  disturbed  crawl  slowly  and 
stupidly  about,  sometimes  even  painfully  attempting  to  perform 
their  usual  duties  of  restoration  and  repair.  We  have  not  explored 
their  nests  in  the  coldest  weather,  when  the  ground  is  frozen 
to  a  considerable  depth. 

During  the  first  warm  days  of  spring  the  thoroughly  awakened 
ants  begin  to  open  up  their  burrows  to  the  surface,  and  carry 
their  own  eggs  and  young  and  the  eggs  of  the  plant  lice  in  their 
possession  upwards  and  downwards  according  to  the  varying 
warmth  of  different  layers  of  the  soil.  When  the  sun  is  shining 
brightly  in  the  middle  of  the  day  they  bring  their  charges  to  the 
more  superficial  chambers  of  their  nests,  or  even  expose  them  on 
the  surface,  but  keep  them  farther  downward  at  night  and  in  cold 
and  cloudy  weather.  The  effect  of  this  care  upon  the  plant-louse 
eggs  is  shown  by  the  earlier  hatching  of  those  cared  for  by  the 
ants,  and  by  the  diminished  number  of  those  which  fail  to  hatch 
at  all. 

Although  this  ant  is  evidently  chiefly  dependent  for  food 
upon  the  corn  root  aphis  and  other  plant  lice  fostered  by  it,  it  is 
not  strictly  limited  to  this  resource  but,  early  in  spring  especially, 
has  been  found  by  us  with  freshly  killed  insects  in  its  possession 
• — caterpillars,  carabid  larvae,  and  the  like.  Sometimes  in  mid- 


256 


BULLETIN   NO.   44. 


[May, 


summer  also  it  resorts  to  animal  food.  July  16,  1884,  in  digging 
into  a  hill  of  corn  infested  by  the  root  aphis  and  this  ant,  I  un- 
earthed a  carabid  larva.  This  was  suddenly  attacked  by  one  of 
the  ants,  which  pounced  upon  it  just  behind  the  head.  The  larva 
struggled  vigorously,  but  the  ant  soon  fastened  its  jaws  on  the 
under  side  of  the  neck,  just  behind  the  head,  and  a  little  to  one 
side  of  the  middle  line.  After  this  the  struggle  lasted  only  a  few 
seconds,  when  the  larva  became  completely  quiet,  and  allowed 
this  ant  and  another  to  drag  it  away  without  the  least  resistance. 
I  watched  this  operation  for  a  few  minutes  with  a  glass,  and  then 
put  both  ants  and  larva  into  alcohol.  Although  the  larva  did  not 
visibly  bleed  when  bitten,  it  was  apparently  dead,  and  did  not 
struggle  at  all  when  put  into  alcohol. 

June  2,  1891,  an  ant  of  the  above  species  (Lasius  niger)  was 
found  with  a  dead  chinch  bug  in  a  wheat  field,  and  three  others 
were  seen  dragging  live  chinch  bugs  over  the  ground,  one  of 
which  bareley  showed  signs  of  life,  a  second  of  which  moved  its 
legs  more  vigorously,  while  a  third,  which  an  ant  was  dragging 
along  by  the  beak,  seemed  scarcely  at  all  disabled. 

THE  GRASS  ROOT  LOUSE. 
{Schizoneura  panicola,  Thos.) 


FlG.  40. — Grass  Root  Louse,  winged  viviparous  female;  enlarged  eighteen  diameters: 

a,  antenna. 

This  species  was  discovered  on  the  roots  of  Panicum  glabrum 
and  other  grasses  by  Mr.  H.  Pergande,  at  St.  Louis,  Mo.,  in 
November,  1877,  and  first  described  by  Dr.  Thomas  in  1879  in  the 
Eighth  Report  of  the  State  Entomologist  of  Illinois.  The  first 
observations  of  its  occurrence  in  this  State  on  corn  were  made  in 
1883,  and  it  has  been  seen  by  us  more  or  less  abundant  on  the 
roots  of  various  plants  every  year  during  the  past  eleven  years. 
Its  economic  importance  is  but  small,  owing  to  the  usually  trivial 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN-  257 

numbers  in  which  it  occurs  on  corn,  and  the  evanescent  character 
of  its  attack.  It  is  often  important,  however,  that  the  corn  farmer 
should  be  able  to  distinguish  it  from  the  far  more  dangerous  corn 
root  aphis — a  matter  of  no  difficulty  to  a  fairly  good  observer.  It 
may  be  told  at  once  from  that  species  by  its  white  or  .yellowish 
color,  and  by  the  absence  of  the  projecting  cornicles  or  honey- 
tubes  characteristic  of  Aphis,  these  being  replaced  in  the  present 
species  by  a  pair  of  minute  circular  openings  on  the  hinder  part  of 
the  back,  each  delicately  rimmed  with  brown,  and  surrounded  by 
a  small  dark  patch. 


FIG.  41. — Grass  Root  Louse,  wingless  viviparous  female  ;  enlarged  29  diameters. 

2.     Roots  evidently  injured  or  destroyed  by  perforations,  gnawing, 

burrowing,  decay,  or  other  loss  of  substance. 

a.  Roots  eaten  away,  not  burrowed  or  perforated,  and  with- 
out rotten  or  withered  tips.  Tap-root  commonly  gone 
or  decayed.  White  grubs  in  soil  among  or  beneath  the 
roots. 

THE  WHITE  GRUBS. 

GENERA  LACHNOSTERNA  AND  CYCLOCEPHALA. 
(Fio.  42-47.) 

White  grubs  or  "grub  worms"  are  among  the  immemorial 
enemies  of  agriculture  on  both  sides  of  the  Atlantic,  and  in  both 
Europe  and  America  the  problem  presented  by  their  injuries  on 
the  farm  and  in  the  fruit  and  vegetable  garden  still  calls  for 
thoroughgoing  investigation  and  scientific  treatment.  In  fact, 
the  steady  increase  of  their  numb'ers  in  this  State — probably  con- 
nected with  the  gradual  enlargement  of  the  area  laid  down  in  grass 
— has  made  such  an  investigation  of  their  life  histories,  habits,  and 
economic  relations  simply  imperative  and  indispensable. 

They  infest  a  great  variety  of  plants,  nearly  all  of  which  have 
an  agricultural  value,  many  of  them  being  the  great  staple  crops 


258  BULLETIN   NO.   44.  \May, 

of  the  farm  and  garden.  Grasses  of  every  kind,  all  the  small 
grains,  Indian  corn,  potatoes,  beets,  and  the  root  crops  generally 
are  liable  to  destruction  by  them,  as  well  as  strawberries  and 
young  fruit  trees,  young  evergreens,  larches,  and  young  forest 
trees  of  various  kinds. 

Like  most  other  injurious  insects  of  the  first  class,  they  are 
liable  to  great  variation  and  fluctuation  of  numbers  in  different 
localities  and  in  successive  years,  sometimes  getting  the  tempo- 
rary mastery  of  a  considerable  tract,  appropriating  nearly  its 
whole  growth  of  vegetation  to  their  own  use,  and  then,  within 
a  year  or  two,  disappearing  from  view  for  a  time  as  an  injurious 
agency.  Apart  from  these  seemingly  spontaneous  fluctuations  of 
numbers,  they  are  most  likely  to  cause  great  loss  when  the  crop 
on  ground  infested  by  them  is  changed  by  rotation  from  one 
affording  them  an  abundance  of  food  to  one  yielding  a  relatively 
scanty  growth — as  when  grass  lands  are  planted  to  corn.  A  num- 
ber of  grubs  which  would  produce  no  visible  effect  in  a  dense 
sward,  may  be  sufficient  to  devour  completely  a  field  of  young 
corn. 

They  hatch  most  commonly  in  grass  lands  (although  frequently 
also  in  corn),  from  eggs  laid  there  by  various  kinds  of  beetles,  all 
commonly  confused  under  the  general  name  of  "June  beetles"  or 
"May  beetles"  or  "dor-bugs."  These  large,  thick,  short,  snuff- 
brown  beetles,  a  half  inch  to  more  than  three-fourths  of  an  inch 
in  length,  nearly  as  thick  from  above  downwards  as  they  are  wide, 
and  about  half  as  wide  as  long,  are  universally  known  because  of 
their  great  abundance  in  May  and  June,  during  which  months 
they  fly  at  night,  filling  the  air  at  dusk  with  their  hoarse  buzzing, 
and  often  invading  lighted  rooms  in  our  houses,  where  they  bump 
and  bumble  about,  as  awkward  as  frolicking  cart  horses.  In  this 
stage  the  insects  are  but  short-lived,  the  males  dying  soon  after 
the  sexes  pair,  and  the  females  living  but  a  few  days  after  they 
have  laid  their  eggs  in  the  ground. 

The  young  grubs  hatching  among  the  roots  of  grass  or  grass- 
like  plants  commence  to  feed  at  once,  and  live  in  the  earth  in  the 
larval  stage  for  at  least  two  years  (so  far  as  known),  most  of  them 
changing  to  the  dormant  pupa  from  the  middle  of  June  to  Sep- 
tember of  the  second  or  third  year  after  hatching,  and  becoming 
fully  developed  "June  beetles"  again,  still  in  the  earth,  in  August 
or  in  September  of  this  same  year.  These  beetles  do  not,  as  a 
rule,  emerge  from  their  earthen  cells  until  the  following  spring, 
but  spend  the  winter  at  rest,  each  in  the  underground  cavity  made 
originally  by  the  grub  while  preparing  to  pupate.  In  May  and 
June  they  come  out  and  pair  and  lay  their  eggs  as  already  related. 


1896.]        INSECT  INJURIES   TO   SEED   AND   ROOT   OF   CORN.  259 

A  single  species  (Cyclocephala  immaculatd)  has  a  slightly  different 
life  history,  the  grub  not  pupating  until  spring.  (Fig.  45-47.) 

Our  common  and  destructive  white  grubs  all  belong  to  the 
genera  Lachnosterna  and  Cyclocephala,  by  far  the  greater  number 
•of  species  and  individuals  to  the  former  genus,  of  which  there  are 
thirty-two  species  known  to  occur  in  Illinois.  The  genus  Cyclo- 
cephala, on  the  other  hand,  contains  but  one  species  in  this  state. 
The  life  histories  of  these  various  kinds  are  not  sufficiently  differ- 
ent to  make  discrimination  of  species  a  matter  of  practical 
importance,  and  for  economic  purposes,  consequently,  the  white 
grubs  may  usually  be  classed  as  one. 

No  wholly,  or  even  fairly,  satisfactory  defence  against  them 
has  yet  been  discovered,  but  in  the  contest  with  so  abundant,  so 
widespread,  and  so  destructive  an  insect  even  imperfectly  pro- 
tective measures,  or  merely  palliative  ones,  are  worthy  of  the 
most  careful  attention.  The  practice  of  the  farmers  of  the  Old 
World,  where  a  contest  against  closely  related  insects  of  like  habit 
has  been  waged  from  time  immemorial,  is  not  usually  applicable 
to  American  agriculture,  but  may  nevertheless  become  so  as  con- 
ditions gradually  change  with  the  denser  settlement  of  this 
country  and  a  corresponding  increase  in  the  value  of  our  agricul- 
tural products.  I  have  consequently  summarized  the  economic 
procedure  of  England,  France,  and  Germany  for  the  "cockchafer 
grub,"  the  " ver  blanc"  and  the  " engerling," — the  names  by  which 
the  European  "white  grubs"  are  known  in  those  countries  re- 
spectively. 

INJURIES   TO   CORN   AND   OTHER   VEGETATION. 

The  injuries  of  the  American  white  grubs  to  corn  may  begin 
as  soon  as  the  roots  of  the  young  plant  become  large  enough  to 
attract  the  attention  of  a  hungry  insect,  and  m'ay  range — accord- 
ing to  the  age  of  the  plant,  the  kind  of  weather,  and  the  age  and 
abundance  of  the  grubs  —  all  the  way  from  a  slight  and  temporary 
retardation  of  growth  to  an  immediate  and  complete  destruction 
of  all  the  corn.  An  early  loss  of  the  tap-root  exposes  the  plant  to 
severe  suffering  by  early  drouth,  and  it  is  often  so  reduced  in 
vigor  from  root  injury  that  it  fails  to  form  brace  roots  at  the 
proper  time,  and  hence  has  so  slight  a  hold  upon  the  earth  that  it 
cannot  keep  itself  erect  or  recover  itself  after  prostration  by  a 
windy  summer  storm. 

In  any  case  where  the  plant  is  yellowed,  or  dwarfed,  or  killed 
outright, — especially  if  these  appearances  be  most  marked  on  the 
higher,  lighter  parts  of  the  field, — the  presence  of  white  grubs 
may  be  suspected. 


26O  BULLETIN  NO.   44. 

As  the  roots  of  an  infested  plant  are  evidently  eaten  away, 
injury  by  the  white  grub  is  not  easily  mistaken  for  any  other, 
and  the  presence  of  the  conspicuous  insects  themselves,  in  the 
earth  among  or  beneath  the  roots,  will  commonly  confirm  the 
diagnosis.  If  they  are  not  thus  found  where  other  evidence  points 
to  them  as  the  cause  of  the  injury,  they  may  frequently  be  dis- 
covered by  digging  down  a  foot  or  two  in  the  worst-injured  tracts. 

As  a  fair  illustration  of  the  extent  and  general  effect  of  a 
severe  attack  on  corn,  our  observations  of  their  work  in  a  twenty- 
acre  field  near  Champaign,  Illinois,  are  worthy  of  detailed  report. 
This  field  of  rich,  black  land  had  been  heavily  fertilized  with  straw- 
pile  manure  and  seeded  to  timothy  in  1884.  It  was  pastured  con- 
tinuously until  1888,  when  it  was  left  for  hay,  yielding  a  good  crop 
of  clean  timothy  that  year.  The  sod  was  broken  in  the  spring  of 
1889,  and  planted  to  corn  May  roth,  immediately  after  breaking. 
This  first  planting  was  taken  by  web  worms  and  cutworms,  but  the 
second  grew  well,  and  promised  an  excellent  crop  until  about 
tasseling  time,  when  the  owner  noticed  that  much  of  the  corn  had 
a  yellowish  and  unhealthy  appearance,  and  that  it  blew  down 
readily  when  the  ground  was  wet.  These  fallen  hills  pulled  up 
easily,  and  the  roots  had  a  stubbed  appearance,  as  if  cut  off  near 
.their  origin.  A  search  in  the  earth  where  the  corn  had  stood  com- 
monly yielded  six  to  twelve  white  grubs  to  a  hill.  The  crop  on 
two  or  three  acres  of  the  highest  land  was  a  total  failure,  and  the 
yield  was  light  on  the  lower  ground. 

The  following  year  (1890)  the  field  was  plowed  April  28th  and 
planted  again  to  corn,  although  an  abundance  of  grubs  were 
noticed  when  the  plowing  was  done.  Several  hundred  were,  in 
fact,  collected  by  us  April  28th  for  breeding-cage  experiments, 
nearly  all  belonging  to  the  species  L.  rugosa  (Fig.  42,  43,  and  44). 
An  estimate  based  at  this  time  on  a  count  of  the  grubs  found 
within  the  length  of  a  rod.  in  a  fourteen-inch  furrow,  gave  between 
six  and  seven  hundred  to  the  square  rod,  or  at  the  rate  of  two 
hundred  and  eighty-eight  pounds  per  acre.  By  the  time  the 
young  corn  was  six  inches  high  about  two-thirds  of  it  had  been 
destroyed  by  the  grubs.  The  field  was  not  replanted,  but  about 
the  loth  of  June  it  was  twice  harrowed  and  sown  to  hemp.  On 
account  of  the  lateness  of  the  season  and  a  midsummer  drouth 
the  hemp  did  not  grow  well,  and  about  a  hundred  bushels  of  corn 
were  finally  taken  from  this  twenty-acre  field.  July  26th,  in  the  part 
of  the  field  which  had  been  worst  infested,  but  three  grubs  and  a 
single  pupa  were  found  in  digging  with  a  spade  twenty  holes, 
ranging  in  depth  from  a  foot  to  twenty-six  inches.  On  the  ist  of 
September  a  trench  four  feet  long,  three  feet  wide,  and  two  feet 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  26l 


deep  was  dug  in  this  same  part  with  the  result  that  only  one  adult 
June  beetle  and  two  long-dead  larvae  were  found.  In  another 
space  eight  feet  long  by  three  feet  wide  two  adults  and  a  single 
living  larva  were  dug  out,  all  the  foregoing  being  within  a  foot  of 
the  surface.  In  two  large  areas  turned  over  at  the  margin  of  the 
worst-infested  spot,  two  living  larvae  and  one  adult  were  taken,  the 
former  among  the  corn  roots  and  the  latter  about  ten  inches  down. 

From  these  field  observations,  and  parallel  extensive  breeding 
operations  in  the  insectary,  we  have  reason  to  infer  the  trans- 
formation to  the  imago  stage  during  the  season  of  1890  of  the 
.greater  part  of  the  white  grubs  in  this  ground. 

In  1891  the  entire  field  was  sown  to  hemp ;  but  in  1892,  three 
years  after  breaking,  it  was  planted  again  to  corn  and  again  heavily 
injured  by  grubs.  August  25th,  a  general  survey  of  the  field 
showed  that  no  part  was  free  from  them,  and  that  probably  every 
acre  had  been  injured  more  or  less.  The  damage  was  most  serious 
now  on  the  lower  ground,  where  a  tract  of  about  two  acres  bore 
only  a  few  scattered  stalks  with  ears.  Most  of  the  corn  here  had 
failed  to  tassel,  and  much  of  it  had  died  when  from  eight  or  ten 
inches  to  about  three  feet  high.  Patches  of  a  rod  to  two  or  three 
rods  across  on  which  the  corn  was  dead  or  worthless  were  to  be 
found  in  all  parts  of  the  field.  Nearly  all  the  foxtail-grass  (Setaria) 
had  also  been  killed,  the  roots  being  cut  off  just  below  the  surface, 
and  even  the  common  purslane  (Portulaca)  was  similarly  de- 
stroyed. Most  of  the  grubs  were  at  this  time  within  three  inches 
of  the  surface,  and  were  well  scattered  through  the  ground,  being 
by  no  means  confined  to  the  hills  of  corn.  In  one  selected  area 
of  four  feet  square,  which  included  only  two  corn  hills,  eighty- 
one  grubs  were  dug  up,  some  scarcely  beneath  the  surface,  and 
none  deeper  than  three  inches.  In  another  area  of  equal  size, 
containing  three  corn  hills,  one  hundred  and  thirty-six  grubs  were 
found,  twenty-one  of  them  in  a  single  hill.  Here,  however,  a  few 
had  burrowed  to  a  depth  of  six  inches.  The  grubs  were  at  this  time 
apparently  from  two-thirds  to  three-fourths  grown,  the  most  abun- 
dant species  being  L.  rugosa — the  same  as  that  of  the  previous  years. 


FIG.   42. —  Grub   of  Lachnosterna   rugosa; 
enlarged  two  and  a  half  diameters. 


FIG.  43. — Last  segment  of  grub, 
seen  from  beneath ;  enlarged 
six  diameters. 


262 


BULLETIN   NO.   44. 


[May. 


In  addition  to  affording  an  excellent  illustration  of  the  destruc- 
tive capacity  of  the  common  white  grubs,  this  record  is  of  special 
interest  as  evidence  that  L.  rugosa  at  least  will  lay  its  eggs  and 
breed  abundantly  in  fields  of  corn.  On  .no  other  supposition  can 
we  explain  the  appearance  of  such  vast  numbers  of  partly  grown 
larvae  three  years  after  the  ground  was  broken  from  grass  in  the 
spring;  three  years,  that  is,  subsequent  to  the  latest  time  at  which 
the  eggs  could  possibly  have  been  laid  in  the  grass.  It  seems  very 
likely  that  this  second  lot  of  grubs  was  hatched  from  eggs  laid  in 
the  corn  in  the  summer  of  1890  by  the  beetles  which  came  out  of  the 
ground  in  this  same  field.  If  this  inference  be  correct,  it  follows 
that  planting  to  hemp  for  a  year  will  not  clear  the  ground  of  grubs. 
A  somewhat  similar  inference  of  a  readiness  to  breed  in  corn 
is  to  be  drawn  from  our  observations  on  another  plat  of  about 
four  acres  on  the  University  farm  near  Urbana.  This  field,  broken 

up  in  the  spring  of  1890  and 
put  into  corn,  was  planted  irt 
1891  partly  to  corn,  and  partly 
to  oats;  in  1892  to  oats  and 
corn  again,  but  with  the  areas 
reversed;  and  in  1.893  to  corn. 
On  this  the  third  year  from 
sod,  more  than  half  the  corn 
fell  flat  on  the  ground  by  the 
middle  of  September,  most  of 
the  roots  being  eaten  off  by 
white  grubs,  of  which  three  or 
four  were  commonly  to  be 
found  in  a  hill.  Owing  to  the 
consequent  weakening  of  the 
plant  the  brace  roots  failed  to- 
form,  the  ears  which  set  were  small  and  very  often  imperfect,  and 
a  large  percentage  of  the  stalks  were  barren,  the  total  height  of 
the  plant  varying  from  six  or  eight  feet  to  less  than  a  foot.  Even 
the  tallest  stalks  were  slender  and  unhealthy  in  appearance,  the 
lower  leaves,  and  sometimes  practically  the  entire  foliage  of  the 
plant,  being  as  dry  and  brittle  as  in  midwinter.  Those  stalks 
which  had  been  killed  early  were  usually  so  decayed  as  to  be 
readily  pulled  apart  at  the  nodes. 

From  these  data  we  must  conclude  that  the  species  concerned 
—  which  was  either  inversa  or  fusca  —  may  live  as  a  larva  through 
four  full  years,  making  the  entire  life  history  cover  a  five-year 
period,  or  else  that  the  eggs  were  laid  later  than  1889  in  either 
corn  or  oats. 


FlG.  44. — Beetle  of  Lachnosterna  rugosa,  male; 
enlarged  two  and  a  fifth  diameters;  a,  last 
two  ventral  segments. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  263 

The  white  grubs  taken  by  us  in  corn  fields  under  circumstances 
to  satisfy  us  that  they  either  were  or  had  been  feeding  on  the 
roots  of  corn  belong  to  eight  species,  as  follows:  Lachnosterna 
fusca,  trtstis,  inversa,  hirticula,  rugosa,  gibbosa,  and  ilicis,  and 
Cyclocephala  immaculata.  Of  these  L.  fusca,  inversa,  and  rugosa 
are  much  the  most  common  in  such  situations;  and  to  them  by 
far  the  greater  part  of  the  damage  done  to  corn  by  the  white 
grubs  in  central  Illinois  must  be  attributed. 

Next  to  Indian  corn,  the  crop  most  generally  and  seriously 
injured  in  Illinois  by  grubs  is  grass;  and  here  the  loss  is  the  more 
serious  because  continuous  and  usually  unnoticed.  A  very  large 
number  of  these  insects  may  live  their  long  lives  in  the  sod,  feed- 
ing steadily  at  the  roots,  and  thus  diminishing  the  yield  without 
actually  deadening  any  continuous  area.  It  is  only  when  through 
uninterrupted  multiplication  they  become  excessively  abundant, 
or  when  severe  drouth  checks  the  growth  of  vegetation,  that 
brown  patches  may  appear  in  midsummer,  sometimes  merging  in 
areas  of  an  acre  or  more  over  which  th'e  turf,  loosened  by  a 
destruction  of  its  roots,  may  be  rolled  up  like  a  carpet. 

That  they  were  original  inhabitants  of  the  wild  prairie  sod  is 
shown  by  the  common  testimony  of  old  settlers,  and  by  Walsh 
in  the  "Practical  Entomologist"  (Vol.  I.,  p.  60),  where  he  reports 
that  in  1845  ne  found  white  grubs  eating  off  young  corn  when  it 
was  a  foot  in  height,  in  a  field  broken  from  prairie  land  the  pre- 
ceding year. 

Patches  of  wheat,  barley,  and  other  small  grains  may  be  simi- 
larly killed,  all  underground  parts  of  the  plant  being  completely 
eaten  up;  but  clover  is  scarcely  ever  damaged  to  any  considerable 
degree,  and  grubs  are  relatively  rare  in  clover  sod  mixed  with 
grass.  Their  injuries  to  potatoes  have  often  been  reported,  and 
are  generally  well  known,  and  they  are  among  the  worst  insect 
enemies  of  the  strawberry  grower.  In  regions  where  the  sugar 
beet  is  an  important  crop,  they  are  among  the  chief  injurious 
insects  to  be  taken  into  account.  Young  larches  and  evergreens 
are  sometimes  killed  by  them  in  the  nursery  rows,  and  probably 
every  kind  of  delicately  rooted  shrub  and  of  young  fruit  and 
forest  tree  is  liable  to  destruction  by  them. 

No  general  list  of  their  food  plants  has  ever  been  prepared, 
and  nothing  whatever  is  known  of  preferences  with  respect  to 
food  among  the  different  species  of  grubs.  That  they  may  live 
for  a  considerable  period  on  earth  alone  is  shown  by  Dr.  Riley, 
who  says  that  he  has  known  the  larvae  of  the  common  May  beetle 
to  feed  for  three  months  on  nothing  but  pure  soil;*  and  Professor 

*St.  Louis  "Globe-Democrat,"  March  25,  1876. 


264  BULLETIN   NO.   44.  [May, 

Perkins,  of  Vermont,  has  kept  individuals  of  all  ages  alive  for 
weeks,  and  sometimes  for  months,  in  sand  more  free  from  organic 
matter  than  the  soil  of  any  field  fit  for  growing  crops.*  The 
remarkable  fact  that  the  grubs  may  eat  locusts'  eggs  in  the  ground 
has  been  mentioned  in  the  First  Report  of  the  U.  S.  Entomologi- 
cal Commission  (p.  305). 

The  beetles  of  the  white  grub  feed  most  frequently  on  the 
leaves  of  various  species  of  trees.  Oak,  hickory,  ash,  box  elder, 
elm,  chestnut,  butternut,  black  walnut,  basswood,  hackberry,  hazel, 
willow,  black  locust,  mountain  ash,  tame  and  wild  cherry,  and  pear 
are  the  species  positively  known  by  us,  by  personal  observation, 
to  be  eaten  by  the  adult  beetles  of  various  species;  and  apple, 
plum,  Lombardy  poplar,  sweet  gum  (Liquidambar),  maple,  and 
birch  may  be  added  to  the  list  on  other  authority.  When  a  tree 
is  much  infested,  the  leaves  are  eaten  entire  except  perhaps  a  stub 
of  the  petiole,  or  the  petiole  and  a  part  of  the  midrib.  Even  the 
bark  of  the  younger  twigs  may  be  gnawed  away.  Two  species, 
hirticula  and  fusca,  have  been  charged  with  an  almost  wanton 
injury  to  the  foliage  of  trees  (oak  and  chestnut)  done  by  gnawing 
through  the  leaf  petioles  without  eating  the  leaves  (Proc.  Ent. 
Soc.  Washington,  Vol.  II.,  p.  59),  and  we  have  noted  the  same 
habit  as  occasionally  exhibited  to  some  small  extent  in  the  "artificial 
forest"  on  the  University  premises  at  Urbana.  The  imagos 
sometimes  eat  the  leaves  of  blue-grass  also,  and  we  have  once 
found  them  feeding  on  heads  of  clover  and  once  on  corn.  Several 
species  have  been  known  to  eat  the  leaves  of  raspberries  ("Insect 
Life,"  Vol.  I.,  p.  366). 

These  notes  on  the  food  of  the  beetles  are  of  interest  because 
of  the  damage  sometimes  done  by  these  insects,  especially  to 
trees  on  lawns,  during  the  brief  period  of  their  excessive  abun- 
dance in  May  and  June,  but  still  more  because  it  is  in  the  adult  stage 
that  the  white  grubs  are  most  susceptible  to  organized  attack.  If 
they  are  ever  thoroughly  mastered  by  the  farmers  of  America,  it 
will  apparently  be  by  concerted  measures,  possibly  supplemented 
by  legal  requirement,  for  the  destruction  of  June  beetles  before 
they  have  laid  their  eggs. 

LIFE   HISTORY   AND  HABITS. 

The  adult  beetles  of  the  more  abundant  genus  Lachnosterna, 
hibernating  in  the  earth  in  the  cells  where  they  originated,  emerge 
in  spring  and  early  summer  at  periods  varying  according  to  the 
species  of  beetle,  the  general  advancement  of  the  season,  and  the 
character  of  the  weather  at  the  time.  Warm  and  genial  days  in 
*Fifth  Ann.  Rep.  Vt.  Agr.  Exper.  Station  (1891),  p.  151. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  265 

spring  often  bring  them  suddenly  out  in  myriads  where  previously 
only  scattered  individuals  have  been  seen,  and  their  flight  at  night 
is  of  course  more  free  when  the  weather  is  warm  than  when  their 
energies  are  chilled  by  cold  and  storms. 

As  a  rule,  the  males  are  not  only  the  first  to  appear,  but  sur- 
pass the  females  in  number,  taking  the  season  through.  They  also 
come  to  lights  much  more  freely  than  the  females,  as  is  shown  by 
a  comparison  of  our  collections  made  at  lights  with  those  made 
the  same  night  from  trees  on  which  the  beetles  were  feeding. 
The  7th  of  May,  1891,  for  example,  a  collection  of  L.  inversa  made 
with  a  lantern  trap  contained  1, 210  males  and  twenty-four  females, 
— a  ratio  of  fifty  to  one, — while  we  took  from  trees  the  same  night 
one  hundred  and  twenty-two  males  and  seventy-three  females — 
less  than  two  to  one.  Taking  all  our  collections  of  this  species  for 
the  summer  of  1891,  we  find  that  in  those  from  lights  (1,418  speci- 
mens) the  males  are  to  the  females  as  fifty-one  to  one,  while  in 
those  from  trees  (271  specimens)  the  ratio  was  one  and  one-half 
to  one.  This  is,  however,  much  greater  than  the  usual  difference 
in  other  Lachnosternas,  the  species  evidently  varying  with  refer- 
ence to  their  sensibility  to  light. 

However  taken  and  at  whatever  part  of  the  season,  it  is  rarely 
that  the  females  exceed  or  even  equal  the  males  in  the  same 
collection.  Throwing  together  2,600  specimens  of  several  species, 
taken  at  frequent  intervals  throughout  the  season  of  1891,  the 
sexes  of  which  we  have  separated,  it  appears  that  the  ratio  of  males 
to  females  at  lights  was  16.5  to  I,  and  from  trees  and  various 
surface  shelters  (839  specimens)  1.3  to  I.  My  data  on  this  subject 
may  be  conveniently  exhibited  in  the  following  tabular  form  : 


At  I 

,ight. 

On  Tr 

ies,  etc. 

Species. 

Dates. 

No.  of 
specimens. 

Ratio  of 
male 
to  female. 

No.  of 

specimens. 

Ratio  of 
male 
to  female. 

Fusca  .          

April  18  —  June    4 

QA. 

2    2 

TO7 

T     1 

April  29  —  June  24 

185 

4   6 

oC2 

I  ^ 

April  29  —  June  28  .  . 

I  4l8 

m  .0 

271 

I   e 

May      7   

I« 

i  .4 

Gibbosa  

May    15  —  June  24.  . 

42 

IS-O 

2O 

2.^ 

The  adult  beetles  emerging  from  the  ground,  flying  about  at 
night*  in  search  of  food,  pair  in  the  trees,  to  which  they  resort  in 
myriads,  and  retreat  again  to  the  earth  by  day.  Their  first  flight 
is  made  in  the  early  evening,  beginning  at  dusk,  as  they  pass  from 

*  A   single  species   has  been    observed  to  fly  by  day   in  Utah.     (Proc.  Ent.  Soc. 
Washington,  Vol.  II.,  p.  241.) 


266  BULLETIN  NO.  44.  [May, 

the  ground  where  they  have  lain  hidden  by  day  to  the  trees  on 
which  they  feed.  With  the  advent  of  day  they  fly  from  the  trees 
to  the  earth,  and  hide  themselves  an  inch  or  less  underground,  or 
sometimes  merely  creep  under  fallen  grass  and  other  similar 
shelter. 

Particulars  concerning  this  retreat  to  their  hiding  places  at 
the  dawn  of  day  are  given  in  notes  made  by  Mr.  John  Marten 
and  Mr.  Philip  Hucke,  detailed  for  night-work  on  June  beetles 
May  19,  1891. 

3:45  a.  m.  Mr.  Hucke  reports  the  occasional  dropping  of  a 
beetle  from  trees  in  the  artificial  forest  (chiefly  butternuts  and 
hickories)  where  these  observations  were  made.  At  4:05,  an  occa- 
sional beetle  still  dropping  to  the  ground  without  making  any 
effort  to  fly.  At  4:10  the  air  suddenly  became  full  of  flying  beetles. 
One  and  then  another  began  to  make  a  buzzing  noise  with  its 
wings,  when,  as  if  at  a  general  signal,  they  deserted  the  trees  in 
thousands,  and  by  4:25  everything  was  still  again  and  nearly 
every  one  was  gone. 

Within  the  woods  the  beetles  flew  to  a  distance  from  the 
trees  about  equal  to  the  height  from  which  they  started,  the  lower 
ones  on  the  trees  making  a  somewhat  longer  flight  proportionally. 
Striking  against  the  weeds  and  undergrowth,  they  folded  their 
wings,  and  by  4:30  o'clock  reached  the  ground  within  a  hundred 
feet  of  the  trees  from  which  they  took  their  flight.  Probably  in  a 
clearer  place  they  would  make  longer  flights. 

The  Egg- — Some  of  the  species  begin  to  lay  their  eggs  in  the 
earth  early  in  June,  and  this  operation  is  in  progress  for  about  a 
month.  The  eggs  are  placed  from  an  inch  to  three  inches  beneath 
the  surface,  each  enclosed  separately  in  a  cavity  just  large  enough 
to  hold  it,  several,  however,  being  frequently  placed  near  each 
other,  but  never,  according  to  our  observations,  in  a  common  cell. 
There  appears  in  no  case  any  special  preparation  of  the  soil  or 
chamber  containing  the  egg,  the  statement  commonly  made  to 
the  effect  that  the  eggs  are  laid  in  a  ball  of  earth  being  clearly 
erroneous.  The  eggs  are  oblong-oval  when  first  deposited,  but 
soon  swell  by  absorption  to  a  nearly  spherical  form.  The  males 
begin  to  die  not  long  after  pairing,  and  the  females  also  perish  as 
their  ovaries  are  spent.  The  eggs  hatch  in  from  ten  to  eighteen 
days,  according  to  our  experiments.  As  the  data  upon  which 
these  statements  are  based  are  few,  they  may  profitably  be  given 
in  some  detail. 

Larval  Period. —  Our  knowledge  of  the  length  of  life  of  the 
white  grubs  in  the  larval  stage  is  based  solely  upon  inferences 
mostly  drawn  from  the  varying  sizes  of  the  grubs  that  appear  in 


1896.]         INSECT   INJURIES  TO   SEED   AND   ROOT   OF   CORN.  267 

collections  made  at  any  given  time.  Since  the  eggs  are  all 
deposited  practically  within  a  month,  and  since  the  larva  grows 
but  slowly,  differences  in  size  due  to  variations  in  time  of  hatching 
must  be  but  small.  It  is  easily  seen,  however,  from  almost  any  large 
collection  made  in  spring  or  early  summer  at  one  time  and  place 
that  grubs  of  the  same  species  or  group  can  be  readily  assorted 
into  two  lots  differing  notably  in  size,  and  never,  so  far  as  my 
observation  goes,  into  more  than  two.*  This  is  readily  to  be  ex- 
plained on  the  supposition  that  the  larger  specimens  are  two  years 
old  that  season  and  that  the  smaller  have  hatched  from  eggs  laid 
the  preceding  summer.  Upon  this  supposition  the  Lachnosterna 
larva  lives  as  a  grub  a  trifle  over  two  full  years,  changes  to  the 
pupa  and  imago  at  the  beginning  of  the  third  year  of  its  life,  and 
emerges  from  the  earth  an  adult,  prepared  to  lay  its  eggs,  at  the 
end  of  this  three-year  period. 

The  growing  grubs  feed,  of  course,  only  during  the  season  of 
growing  vegetation,  usually  retiring  from  the  middle  to  the  last  of 
November  to  a  depth  beneath  the  surface  varying  according  to 
the  severity  of  the  winter  weather,  and  coming  up  again  within 
reach  of  food  commonly  some  time  in  March  or  early  April. 

The  time  and  place  of  hibernation  have  their  especial  economic 
interest,  since  while  in  their  usual  winter  quarters  the  white  grubs 
are  far  beyond  the  reach  of  any  agricultural  operations.  The  dis- 
tance to  which  they  retreat  in  this  latitude  is  about  a  foot  and  a 
half,  if  I  may  judge  from  a  single  observation  made  November  29, 
1886,  in  a  badly  infested  field  of  wheat  in  Sangamon  county,  Illi- 
nois. Here,  around  the  margins  of  denuded  patches, — the  ground 
being  frozen  some  four  inches  deep, — the  white  grubs  were  found 
repeatedly  in  numbers  averaging  four  or  five  to  the  square  foot  at 
a  depth  varying  from  a  foot  and  a  half  to  two  feet.  In  1890  they 
had  already  come  up,  in  the  pastures,  from  their  winter  quarters 
by  the  24th  of  March ;  were  still  at  the  surface  in  their  usual  num- 
ber during  the  latter  part  of  October;  and  had  not  wholly  with- 
drawn by  November  2$th — although  at  this  last  date  most  had  gone 
beyond  the  reach  of  the  plow.  Notwithstanding  this  well-marked 
habit  of  retreat  at  the  approach  of  winter,  they  occasionally  linger 
at  the  surface  and  hibernate  at  a  depth  scarcely  greater  than  that 
at  which  they  are  to  be  found  during  the  summer  season. 

Pupation  and  Formation  of  the  Beetle. — The  full-grown  white 
grubs,  presumed  to  be  two  years  old  according  to  the  preceding 
section,  will  live  an  active  life  in  the  earth,  feeding  freely  from 

*  To  verify  this  statement  it  is  necessary  that  the  observer  should  learn  to  dis- 
tinguish species  or  at  least  groups  of  species  of  these  insects  in  the  grub  and  larval 
stage. 


268  BULLETIN   NO.   44.  \May, 

March  to  June  or  July,  during  which  months  they  change  to  the 
pupa  a  few  inches  under  ground,  in  oval  cells  made  by  the  grub  by 
turning  about  in  the  earth.  In  this  smooth-walled  chamber  the 
cuticular  remnant  of  the  last  moult  will  be  found  enclosed  with  the 
pupa — that  is,  the  crust  of  the  head  of  the  grub  and  shriveled  frag- 
ments of  its  last  skin.  Our  first  date  for  this  pupal  transformation 
of  L.  inversa  is  June  13,  1889,  but  Professor  Perkins  notes  the 
pupation  of  two  larvae  out  of  several  hundred  early  in  May.  In 
this  chamber  they  lie  until  August  or  September,  when  they 
change  to  the  June  beetle,  fusca  and  gibbosa  as  early  as  August 
nth,  and  others — at  least  individuals  of  implicita,  for  example — 
not  before  September  i/th.  A  small  percentage  of  the  adults 
thus  formed  late  in  the  summer  and  in  early  fall,  may  escape  from 
the  earth  before  the  winter  opens,  but  this  is  relatively  a  rare 
occurrence,  the  great  mass  of  the  generation  continuing  through 
the  winter  in  the  pupal  cells  within  which  they  originated.  They 
are  to  be  found  in  winter  from  no  more  than  two  or  three  inches 
to  about  ten  inches  beneath  the  surface.  Hence  they  escape  in 
spring,  as  already  described,  pairing  and  laying  their  eggs  for  the 
generation  following. 

From  the  foregoing  it  will  be  seen  that  the  white  grubs  of  the 
genus  Lachnosterna  hibernate  in  two  stages  only,  those  of  larva 
and  imago,  the  grubs  themselves  representing  at  least  two  gen- 
erations. 

Cyclocephala.  (Fig.  45-47.) — The  white  grubs  of  the  genus 
Cyclocephala  differ  from  those  of  the  various  species  of  Lachno- 
sterna in  so  far,  at  least,  as  to  hibernate  in  the  larval  stage,  to 
pupate  in  May  and  June,  and  to  emerge  as  beetles  in  June  and  July 
— later  on  an  average  than  the  species  of  the  other  genus.  Pupa- 
tion is  consequently  earlier  than  in  Lachnosterna,  and  the 
emergence  of  the  imago  occurs  later  in  the  season,  the  essential 
difference  being  that  adults  of  Cyclocephala  escape  from  the  earth 
one  or  two  months  after  the  completion  of  their  larval  life,  while 
those  of  Lachnosterna  continue  in  the  earthen  cells  as  pupae  and 
images  about  ten  months.  The  difference  in  the  economic  appli- 
cation of  these  biographies  is  not,  however,  very  great,  since  the 
period  of  active  larval  life  of  Cyclocephala  seems  to  terminate  on 
an  average  only  three  or  four  weeks  before  that  of  Lachnosterna. 
My  detailed  notes  on  the  transformation  of  white  grubs  belonging 
to  this  genus  are  but  few  in  number,  but  as  they  accord  with  those 
already  given  by  entomologists,  they  serve  to  support  the  common 
statements  concerning  the  life  history  of  these  beetles. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  269 


Our  only  species  in  Illinois  is  C.  immaculata,  and  its  larvae 
occur  in  grass  with  the  other  white  grubs,  and  have  been  found 
infesting  corn  on  sod. 


FIG.  45. — Grub  of  Cyclocephala  immaculata;   en- 
larged three  and  a  third  diameters. 


FIG.  46. — Last  segment  of  grub, 
seen  from  beneath ;  enlarged 
six  diameters. 


NATURAL   ENEMIES. 

In  the  struggle  for  existence  the  white  grubs  and  the  June 
beetles  enjoy  many  pronounced  advantages,  and  are  subject  to 
relatively  few  and  feeble  checks  on  their  multiplication.  The  large 
size  and  the  subterranean  habit  of  the  grubs  protect  them  in  great 

measure  against  two  of  the  three  prin- 
cipal classes  of  natural  enemies  of  insect 
larvae ;  namely,  birds  and  insect  para- 
sites. They  are  more  liable  to  fungus 
parasitism,  it  is  true,  but  many  kinds  of 
much  less  abundant  insects  suffer  far 
more  heavily  therefrom,  and  authentic 
reports  of  the  notable  destruction  of  our 
American  white  grubs  by  fungus  para- 
sites are  rare.  The  beetles  are  espe- 
cially protected  by  their  large  size  and 
heavy  armor,  by  their  nocturnal  habit 
and  their  skill  in  hiding  themselves  by  day,  by  the  enormous 
numbers  in  which  they  appear,  and  by  the  relatively  short  term  of 
their  adult  life.  Cold  and  heat,  drouth  and  wet  weather  have  little 
noticeable  effect  upon  these  insects  in  any  stage,  and  even  star- 
vation does  not  kill  the  grubs,  for  in  the  absence  of  other  food  they 
can  live  for  months  on  earth  alone. 

Great  as  the  number  doubtless  is  of  individuals  of  the  several 
species  which  fall  victims  during  the  year  to  various  enemies  and 
other  hostile  agencies,  the  evidence  now  before  us  does  not  warrant 
us  in  placing  any  considerable  reliance  on  these  natural  checks  to 
the  multiplication  of  the  white  grubs,  but  we  are  rather  led  to  con- 
clude that  American  agriculture  must  look  to  its  own  resources  for 


FIG.  47. — Beetle  of  Cyclocephala 
immaculata;  enlarged  three 
diameters. 


270  BULLETIN  NO.  44.  [May, 

a  remedy.  If,  however,  we  take  into  account  the  fact  that  our 
common  white  grubs  are  native  insects,  most  of  them  living 
originally  in  the  prairie  sod,  which  formed  a  denser,  more  uniform, 
and  more  continuous  covering  to  the  surface  of  the  country  than 
the  crops  now  raised  by  the  farmer,  and  further  recall  the  fact  that 
under  these  primitive  conditions  these  insects  rarely  produced  any 
conspicuous  effect  upon  our  native  vegetation,  we  may  infer  with 
some  confidence  that  they  are  not  likely  to  increase  indefinitely 
and  inordinately,  but  that  the  natural  checks  which  held  them 
primitively  within  a  certain  well-defined  limit  will  reassert  them- 
selves under  the  not  very  different  conditions  of  a  developed  agri- 
culture. Such  data  as  we  have  concerning  the  enemies  of  these 
insects,  animal  and  vegetable,  are  presented  here  more  as  an 
indication  of  the  incompleteness  of  our  knowledge,  than  because 
of  their  present  practical  value. 

Birds. — White  grubs  and  June  beetles  are  eaten  to  some 
extent  by  a  considerable  variety  of  birds,  doubtless  by  many  more 
than  my  cullings  of  the  scanty  literature  of  this  subject  have 
brought  to  light. 

In  my  own  studies,  I  have  found  June  beetles  eaten  by  the 
robin,  catbird,  brown  thrush,  wood  thrush,  hermit  thrush,  blue- 
bird, and  meadow  lark;  Mr.  E.  V.  Wilcox  has  found  both  June 
beetles  and  white  grubs  in  the  stomachs  of  robins  ;  and  Glover 
long  ago  recorded  the  occurrence  of  June  beetles  in  the  stomach 
of  a  woodpecker  (Rep.  U.  S.  Comm.  Agr.  1865,  p.  38).  Dr.  A.  K. 
Fisher  reports  the  occurrence  of  these  beetles  in  the  food  of  the 
red-tailed  hawk,  the  red-shouldered  hawk,  the  broad-winged 
hawk,  the  sparrow  hawk,  the  screech  owl,  and  the  great  horned 
owl;  and  white  grubs  in  that  "of  the  red-shouldered  hawk,  the 
sparrow  hawk,  and  the  barred  owl.  Dr.  C.  V.  Riley's  assistants 
recognized  fragments  of  the  beetles  in  the  stomachs  of  six  English 
sparrows,  and  four  large  white  grubs  in  one  of  this  species,  out  of 
five  hundred  and  twenty-two  specimens  examined. 

To  this  list  I  can  add  only  the  crow  and  the  blue  jay,  on  the 
authority  of  Dr.  B.  H.  Warren,  author  of  the  "  Birds  of  Pennsyl- 
vania," the  chuck-will's  widow  ("Insect  Life,"  Vol.  II.,  p.  189),  the 
king-bird  (Lintner),  and  the  crow  blackbird,  whose  habit  of  picking 
up  white  grubs  after  the  plow  is  a  matter  of  common  observation. 

Of  these  twenty  species,  taking  into  account  their  numbers 
and  their  feeding  habits,  I  judge  that  the  robin,  the  catbird,  the 
brown  thrush,  and  the  crow  blackbird  devour  much  the  largest 
numbers  of  these  insects,*  although  it  is  possible  that  if  the 

*Nine  out  of  forty-four  robins  shot  by  me  in  April,  May,  and  June  had  eaten  June 
beetles;  six  catbirds  out  of  forty-one:  and  twelve  brown  thrushes  out  of  forty  three 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  271 

smaller  insectivorous  hawks — the  sparrow  hawk  especially — were 
permitted  to  increase  freely  they  would  equal  or  surpass  any  of 
these,  because  of  the  greater  number  of  insects  which  they  take 
at  a  meal.  Chickens,  ducks,  and  turkeys  are  fond  of  white  grubs, 
and  may  often  be  seen  scattered  over  freshly  plowed  ground  in 
search  of  them  and  other  subterranean  insects. 

Mammals. — The  only  native  mammals  known  to  feed  on  these 
insects  in  any  considerable  numbers  are  moles,  ground  squirrels, 
and  skunks — none  of  them  very  likely  to  be  tolerated  by  the 
farmer,  whatever  may  be  their  insectivorous  habits. 

Among  the  domestic  animals,  pigs  are  well  known  as  eager 
hunters  for  white  grubs,  in  search  of  which  they  dilligently  root 
up  an  infested  turf;  a  fact  which  may  sometimes  be  advantageous- 
ly applied  for  the  protection  of  corn  to  follow  upon  grass. 

Insects. — The  special  insect  enemies  of  the  white  grubs  now  on 
record  belong  to  three  or,  possibly,  four  species,  two  of  them 
hymenopterous  and  one  dipterous,  a  second  dipterous  insect  bred 
by  us  from  dead  white  grubs  being  doubtfully  parasitic.  To  this 
number  I  am  able  to  add  another  hymenopterous  parasite,  Pelecinus 
polyturator,  a  remarkable  insect  whose  larval  history  has  hereto- 
fore been  wholly  unknown.  From  a  collection  of  white  grubs 
obtained  from  an  orchard  at  Champaign,  Illinois,  May  9,  1892,  and 
kept  in  a  breeding  cage  at  my  office  inscctary,  a  specimen  of 
Pelecinus  polyturator  emerged  August  26,  1892.  As  the  parasite 
was  seen  in  the  act  of  emerging  from  its  pupal  envelope,  there  can 
be  no  doubt  of  either  the  fact  or  the  date.  An  examination  of 
the  remains  of  the  grub  containing  the  pupa  skin  of  the  parasite 
showed  that  the  former  belonged  to  the  species  L.  gibbosa.  My 
office  specimens  of  the  adult  of  this  parasite  are  recorded  under 
nine  collection  numbers,  all  bearing  dates  in  late  summer  and 
«arly  fall — July  2ist,  26th,  August  1st,  2d,  nth,  i6th,  28th,  and 
September  ist  and  i6th.  It  is  hence  probably  single  brooded, 
maturing  in  July  and  August. 

Perhaps  the  most  destructive  insect  enemy  of  the  white  grub 
is  Tiphia  inornata,  Say,  a  hymenopterous  species  which  we  have 
never  bred,  but  which  has  been  reported  by  Dr.  Riley  to  occur 
occasionally  in  very  large  numbers  in  ground  infested  by  Lach- 
nosterna  larvae.  He  says:  "  One  can  scarcely  dig  for  half  an 
hour  in  any  soil  in  this  part  of  the  country,  without  meeting  with 
a  curious  egg-shaped  cocoon,  of  a  pale  golden  brown  or  buff  color, 
and  with  a  soft  exterior  surface,  in  touch  as  well  as  in  color  remind- 
ing* one  of  the  punk  used  by  dentists.  Upon  cutting  this  cocoon 
open,  it  will  be  found  to  consist  of  about  a  dozen  delicate  layers, 
the  outer  ones  soft  and  loosely  spun,  the  inner  ones  more  and 


2/2  BULLETIN   NO.   44.  [May, 

more  compact  and  paler  in  color.  Within  this  cocoon,  if  fresh, 
there  will  be  found  a  whitish  grub  which,  though  lacking  legs,  has 
the  joints  of  the  body,  at  the  sides,  swollen  so  as  to  look  like  the 
fleshy  pseudopods  possessed  by  many  larvae.  *  *  *  From  hav- 
ing repeatedly  found  the  head  parts  of  some  Lamellicorn  larva 
attached  to  these  cocoons,  I  had  long  suspected  that  such  larvae 
formed  the  food  of  this  Tiphia,  and  on  carefully  examining  these 
head-parts  I  recognized  them  as  belonging  to  the  common  white 
grub.  But  all  doubt  as  to  this  fly's  being  parasitic  on  said  white 
grub  ceased  when,  in  1872,  Mr.  A.  W.  Smith,  of  St.  Louis,  brought 
me  a  number  of  the  cocoons  which  he  had  taken  from  a  low  part 
of  his  farm  on  the  Illinois  bottom,  where  the  white  grub  was  very 
thick,  and  the  yellow  cocoons  so  numerous  as  to  attract  attention. " 

Ophion  bifoveolatum  is  likewise  reported  by  Riley  as  a  white 
grub  parasite  (Proc.  Ent.  Soc.  Washington,  Vol.  II.,  p.  134),  and 
this  was  quite  probably  the  species  of  Ophion  bred  at  my  office  in 
1886.  From  white  grubs  brought  to  the  insectary  April  27th  the 
specimen  emerged  May  nth,  but  was  lost  from  my  collections 
before  being  determined  specifically. 

A  tachinid  fly  has  also  been  found  parasitic  on  the  grubs 
(Proc.  Ent.  Soc.  Washington,  Vol.  II.,  p.  134),  and  a  second  fly, 
Microphthalma  nigra,  Macq.,  has  been  repeatedly  bred  by  us 
from  the  dead  bodies  of  white  grubs.  The  habits  of  the  family 
Dexidae,  to  which  this  last  mentioned  insect  belongs,  make  it 
doubtful,  however,  if  these  flies  may  not  have  developed  from 
eggs  laid  on  the  bodies  of  grubs  already  dead. 

Tiphia  inornata,  mentioned  above,  ought  probably  to  be 
called  a  predaceous  rather  than  a  parasitic  insect,  as  it  attacks  the 
grub  from  without,  and  devours  it  bodily.  Ants  destroy  white 
grubs  in  breeding-cages,  and  very  possibly  attack  them  sometimes 
in  the  field.  It  is  quite  likely  that  various  other  predaceous  insect 
species,  ground  beetles  especially,  may  devour  white  grubs  occa- 
sionally, as  has  indeed  been  suggested  by  Riley  (Sixth  Ent.  Rep. 
Mo.),  but  I  have  no  record  of  precise  observations  to  that  effect. 
The  fact  that  the  beetles  may  sometimes  fall  a  prey  to  carnivorous 
insects,  is  shown  by  two  specimens  brought  to  my  office  by  a 
student  of  the  University,  May  21,  1891.  One  of  these  was  an 
example  of  L.  hirticula,  which  he  had  found  with  the  tip  of  its 
abdomen  torn  open,  crawling  up  a  stem  of  grass.  The  other  was 
a  Chlcenius  tomentosus,  found  clinging  to  the  Lachnosterna  and 
feeding  upon  its  viscera,  partly  drawn  out  of  the  wound.  The 
frequency  with  which  mites  are  found  clustered  upon  white  gr*ubs 
in  their  earthen  cells,  especially  upon  those  recently  dead  or  in 
a  weakened  condition,  has  given  rise  to  the  supposition,  hitherto 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  2/3 

not  experimentally  verified,  that  these  mites  may  be  parasitic  on 
the  grubs. 

On  the  whole,  the  general  tenor  of  our  own  observations,  as 
well  as  those  published  by  other  entomologists,  must  lead  us  to 
attach  comparatively  little  economic  importance  to  the  insect 
enemies  of  white  grubs,  whether  predaceous  or  parasitic. 

Reptiles  and  Amphibians. — The  fact  that  the  toad  occasionally 
eats  June  beetles  has  been  reported  (Proc.  Ent.  Soc.  Washington, 
Vol.  I.,  p.  69),  and  could  no  doubt  be  verified  extensively  by  dis- 
sections of  toads  made  at  times  when  the  June  beetle  is  abroad. 
Frogs  must  likewise  be  placed  on  the  list  of  the  natural  enemies 
of  these  beetles.  Prof.  Perkins,  of  the  University  of  Vermont, 
has  found  as  many  as  ten  in  the  stomath  of  a  single  frog  of  medium 
size.  It  is  altogether  likely  that  insectivorous  reptiles,  serpents 
especially,  would  be  found  to  destroy  a  still  greater  number  of 
these  insects,  but  no  studies  have  been  made,  to  my  knowledge, 
on  this  point. 

Fungi. — But  one  contagious  disease  of  the  American  white 
grub  occurring  in  nature  has  been  positively  and  definitely  con- 
nected with  a  fungus  parasite.  This  parasite  (Cordyceps  melolon- 
thce)  has  been  several  times  referred  to  in  economic  literature, 
first  in  the  "American  Journal  of  Science  and  Arts"  (August, 
1824).  It  was  treated  at  length  in  an  illustrated  article  published 
by  Riley  in  the  "American  Entomologist "  for  June,  1880.  Accord- 
ing to  a  correspondent  of  Walsh's  in  1869,  it  has  sometimes  been 
very  common  in  Virginia ;  and  Mrs.  Treat  reported  the  occurrence 
of  thousands  of  infested  specimens  in  Benton  county,  Iowa,  in 
1865.  Perkins  mentions  it  as  infesting  grubs  of  Lachnosterna  in 
Vermont.  This  species  is,  so  far  as  known,  incapable  of  artificial 
cultivation,  and  could  consequently  be  used  for  insecticide 
purposes  only  by  distributing  as  carriers  of  infection  white  grubs 
which  had  been  in  contact  with  others  infested  with  it.  Indica- 
tions have  not  been  wanting  of  the  occurrence  of  a  bacterial  disease 
native  to  our  Lachnosterna  larvae,  but  no  precise  studies  have  been 
made  sufficient  to  warrant  the  assertion  that  such  bacterial  diseases 
really  occur.  The  common  insect  parasite,  Sporotrichum  globu- 
liferum,  the  so-called  white  fungus  of  the  chinch  bug,  has  never 
been  found  by  us  infesting  Lachnosterna  larvae  in  a  state  of  nature, 
although  these  larvae  have  been  proven  quite  susceptible  to  it  in 
the  course  of  our  experimental  work.  June  beetles  have  been 
frequently  found,  however,  with  this  fungus  growing  upon  their 
dead  bodies,  but,  for  all  that  is  clearly  known  to  the  contrary,  it 
may  have  taken  its  start  upon  them  after  the  death  of  the  beetles. 

In  Europe,  according  to  Giard  and   Krassilstschik,   three  dis- 


274  BULLETIN  NO.   44.  [May, 

eases  of  the  European  white  grubs  have  been  detected:  one  of 
them  due  to  a  fungous  infection  by  the  species  most  commonly 
known  as  haria  densa,  Link,  (=Botrytis  tenella,  Saccardo);  and 
the  other  two,  bacterial  diseases  studied  by  the  last  named  author. 

PREVENTIVE   AND   REMEDIAL   MEASURES. 

If  we  use  the  word  remedy  for  measures  intended  to  arrest  an 
injury  already  begun,  and  prevention  for  measures  applied  in 
advance  of  such  injury,  we  must  say  that  efficient  remedies  for 
the  injuries  of  white  grubs  are  but  little  applicable  to  their  work 
in  corn,  and  that  we  are  confined  consequently,  for  the  main  pur- 
poses of  this  article,  to  a  discussion  of  preventive  measures  only. 
Such  measures  of  prevention  may  be  either  local  or  general: 
applied,  in  the  first  case,  to  the  field  in  which  corn  is  to  be  planted, 
and  intended  to  forestall  injury  in  that  field  only;  or,  in  the  second 
case,  applied  elsewhere  or  more  comprehensively,  with  a  view  to 
a  more  general  effect  in  reducing  the  number  of  white  grubs  over 
a  larger  area. 

Local  preventive  measures  can  take  effect  only  on  the  white 
grubs  themselves,  while  the  most  valuable  general  measures  are 
those  directed  to  the  destruction  of  the  June  beetles  before  their 
eggs  are  laid. 

Local  Prevention. —  It  is  now  well  settled,  as  has  been  shown 
in  the  preceding  pages,  that  at  least  some  species  of  the  white 
grubs  may  be  freely  and  abundantly  bred  in  fields  of  corn;  but  it 
still  remains  true  that  by  far  the  greater  number  of  those  in  the 
country  at  any  time  have  arisen  from  eggs  laid  by  the  beetles  in 
ground  bearing  a  crop  of  grass;  and  that  corn  is  consequently 
much  more  likely  to  be  damaged  if  planted  on  sod  than  if  it  fol- 
lows clover,  some  small  grain,  or  corn  itself.  The  first  effort  of 
the  corn  farmer  threatened  by  these  insects  should  consequently 
be  directed  to  clearing  the  grubs  out  of  the  grass  land  which  he 
wishes  to  plant  to  corn.  For  this  purpose  it  is  very  desirable  that 
hogs  should  be  pastured  for  a  considerable  time  on  meadows  or 
pastures  before  plowing  for  corn,  and  that  they  should  also  be 
given  the  run  of  the  field  while  it  is  being  plowed.  This  measure 
will  be  practically  useless,  however,  under  ordinary  circumstances, 
if  resorted  to  later  than  October  or  earlier  than  April,  as  in  the 
interval  between  these  months  the  grubs  will  be  beyond  the  reach 
of  pigs,  buried  in  their  winter  quarters. 

Further,  I  do  not,  myself,  in  the  least  doubt  the  great  profit 
to  the  average  farmer  of  providing  for  the  collection  of  white 
grubs  after  the  plow,  by  hand,  in  soil  where  they  are  particu- 
larly abundant,  especially  where  any  kind  of  cheap  labor  may 


l8g6.J        INSECT  INJURIES  TO   SEED   AND   ROOT   OF   CORN.  275 

be  had.  In  estimating  the  value  of  this  method,  we  should  bear 
in  mind  the  fact  that  a  small  number  of  grubs  may  do  a  great 
amount  of  harm  to  young  corn  on  comparatively  clean  ground, 
because  of  the  small  amount  of  vegetation  offered  to  them  as 
food  while  the  corn  is  young. 

Next,  we  should  take  into  account  the  relatively  small  damage 
done  to  clover  by  the  grubs,  and  the  further  fact  that  we  have  no 
present  evidence  that  the  eggs  of  the  June  beetle  are  ever  laid  in 
clover  land.  It  is  consequently  a  good  practice,  so  far  as  grub 
injury  is  concerned,  to  insert  clover  (sown  perhaps  with  oats) 
between  grass  and  corn  in  the  rotation  ;  and  this  is  especially  to  be 
advised  on  light  soils,  not  perfectly  adapted  to  corn.  Here  it  will 
have  the  effect  not  only  to  eliminate  the  grubs  in  part,  but  also  to 
diminish  the  damage  to  the  following  crops  of  corn  by  increasing 
the  strength  of  the  land,  thus  helping  the  corn  plant  to  withstand 
such  loss  of  roots  as  it  may  nevertheless  be  subjected  to.  In  this 
connection  it  need  hardly  be  said  that  a  generous  treatment  of  the 
soil  by  heavy  fertilization,  thorough  cultivation,  and  the  like,  will 
diminish  loss  to  corn  by  enabling  plants  attacked  to  throw  out  new 
roots  more  vigorously  to  take  the  place  of  those  eaten  by  the 
grubs.  Indeed,  by  some  most  intelligent  and  successful  farmers, 
high  fertilizing  with  frequent  rotation  is  regarded  as  the  essential 
and  sufficient  defense  against  these  insects. 

The  management  of  corn  on  lands  containing  grubs  should 
also  be  directed  especially  to  the  protection  of  the  plant  from 
drouth,  as,  in  the  presence  of  these  insects,  dry  weather  takes  a 
double  effect  by  retarding  root  growth  under  circumstances  which 
require  it  to  be  vigorously  stimulated  instead. 

To  prevent  the  laying  of  the  eggs  of  the  June  beetle  in  the 
corn  field in  May  or  June,  it  is  desirable  that  the  ground  should  be 
kept  practically  free  from  weeds  at  that  time,  as  it  is  well  known 
that  a  surface  growth  of  vegetation  is  a  strong  attraction  to  these 
insects  searching  for  places  suitable  for  the  support  of  the  young. 
Some  of  our  more  recent  observations  show  that  the  beetles  are 
likely  to  deposit  their  eggs  in  the  field  from  which  they  themselves 
have  emerged,  provided  that  it  offers  them  suitable  conditions — a 
fact  which  makes  it  clearly  inadvisable  that  a  field  which  is  badly 
infested  one  year,  should  be  planted  to  corn  the  next. 

General  Prevention. — The  principal  and  most  effective  prevent- 
ive measures  of  general  promise  are  those  for  the  collection  and 
destruction  of  the  June  beetles  before  they  have  laid  their  eggs. 
They  are  practically  confined  to  the  following  four  methods,  men- 
tioned in  the  order  of  their  importance :  (a)  shaking  and  jarring 
down  the  beetles  at  night  from  the  trees  in  which  they  feed,  and 


276  BULLETIN  NO.   44.  {May, 

their  collection  on  sheets  or  cloth-covered  frames  similar  to  those 
in  use  for  the  peach  and  plum  curculio;  (b)  exposing  light  traps 
early  in  the  evening  in  places  frequented  by  the  beetles;  (c)  the 
spraying  of  trees  to  which  they  resort,  with  Paris  green  or  other 
suitable  insecticide ;  and  (d)  the  turning  of  pigs  into  woodlands, 
forest  plantations,  and  the  like,  where  the  June  beetles  conceal 
themselves  by  day. 

These  are  all  measures  calling  for  cooperative  action  by  all,  or 
at  least  the  greater  part,  of  the  farmers  of  a  neighborhood,  since 
it  is  useless  to  expect  any  pronounced  effect  from  isolated  and 
individual  action.  They  can  only  be  carried  out  by  previous 
agreement  of  those  interested,  by  the  offer  of  premiums  for  the 
beetles,  or  by  the  passage  and  enforcement  of  laws  bearing  equally 
upon  all.  In  estimating  the  value  of  these  methods  it  should  be 
remembered  that  each  female  beetle  is  the  average  equivalent  of 
a  large  number  of  grubs. 

In  illustration  of  the  effectiveness  of  the  first  mentioned  of 
these  methods,  I  quote  from  notes  of  Assistants  Marten  and 
Hucke,  made  in  1891. 

May  igth,  2:40  a.  m.  Shaking  the  trees  in  the  University 
forest  plantation  made  the  beetles  fall  very  easily,  the  second 
shake  generally  getting  all,  or  nearly  all,  there  were  in  a  tree. 
Those  shaken  from  the  trees  made  no  effort  to  fly  up  again,  and 
only  one  such  came  to  the  lantern  trap  near  by. 

3:45  a.  m.  The  beetles  apparently  as  abundant  as  ever  on 
butternut  and  hickory.  The  lightest  shake  of  either  of  these 
trees  brings  down  the  beetles  by  dozens.  Butternut  trees  six  to 
eight  inches  in  diameter  drop  them  in  considerable  numbers  when 
shaken  by  the  hands — so  easily  are  they  detached. 

From  other  notes  it  is  apparent  that  the  June  beetles  cling 
more  closely  to  the  trees  early  in  the  evening, — from  eight  to  ten 
o'clock, — a  fact  doubtless  to  be  connected  with  the  gradually  stupe- 
fying effect  of  the  night  dews  and  the  cooler  air  towards  morning. 

This  is  the  standard  method  in  both  France  and  Germany  for 
the  control  of  injuries  by  the  European  white  grubs.  The  results 
attained  in  the  former  country  are  shown  by  an  article,  "  La 
Chasse  aux  Hannetons,"  published  in  the  Revue  de  deux  Mondes 
for  1878.  In  consequence  of  an  offer  of  premiums  for  beetles  in 
the  department  of  Seine- Inferieure,  1,149,000,000  of  these  cock- 
chafers were  collected  and  paid  for  in  that  year,  at  an  expenditure 
of  $16,000.  It  was  estimated  that  these  beetles  would  have  given 
origin  the  following  year  to  23,000,000,000  white  grubs.  The 
proprietor  of  an  establishment  for  the  manufacture  of  sugar  from 
beets,  whose  crop  was  seriously  affected  by  the  ravages  of  the 


I896.J         INSECT   INJURIES  TO   SEED   AND   ROOT   OF   CORN.  277 

grubs,  offered  a  prize  of  $4  for  each  one  hundred  kilogrammes 
(about  two  hundred  and  twenty  pounds  avoirdupois)  of  the  beetles, 
and  obtained  as  a  consequence  28,000,000  cockchafers — equivalent 
to  560,000,000  grubs  the  following  year. 

Details  of  the  common  procedure  in  France  are  given  by  A. 
Walle's  in  "  Bulletin  de  la  Socie'te  Centrale  d'Apiculture  et  d'ln- 
sectologie"  for  June,  1890.  "  It  would  be  a  mistake,"  he  says,  "to 
wait  until  the  cockchafers  [English  name  for  the  European  equiva- 
lent of  our  June  beetles]  have  emerged,  since  the  whole  benefit 
of  the  capture  of  the  beetles  will  be  lost  if  the  females  are  given 
time  to  lay  their  eggs.  Measures  for  the  destruction  of  these 
insects  must  be  taken,  consequently,  from  the  time  that  a  few 
begin  to  appear.  Further,  if  in  certain  parts  of  the  territory 
involved  the  capture  of  the  beetles  is  neglected,  the  good  effect  of 
the  procedure  will  be  considerably  diminished.  These  two  points 
are  essential  and  imperative. 

"The  cockchafer  catchers  should  be  provided  with  hooked 
poles,  with  an  awning  cloth,  or  the  like,  and  with  bags  for  their 
catch.  It  will  be  well  for  them  to  go  in  little  groups,  and  to  make 
their  rounds  from  the  time  of  the  first  appearance  of  the  insect. 
This  last  observation  is  most  important.  On  the  I2th  of  May,  for 
example  [in  France],  no  more  than  twenty  per  cent,  of  the  cock- 
chafers captured  in  the  trees  will  be  females.  A  little  later,  on 
the  contrary,  the  males  will  have  disappeared,  and  scarcely  any 
but  females  will  be  found.  These,  however,  will  have  laid  their 
eggs. 

"The  beetles  may  be  most  easily  shaken  down  from  the  trees 
in  which  they  are  concealed,  at  the  dawn  of  day,  when  they  are 
still  stupid  with  the  coolness  of  the  night,  and  this  is,  consequently, 
the  time  at  which  these  collections  should  be  made.  Two  persons 
will  do  well  to  work  together  when  tall  trees  are  to  be  visited. 
One  strikes  the  branches  and  shakes  them  by  means  of  the  hook 
fastened  into  the  end  of  his  pole,  while  the  other  picks  up  the 
beetles.  They  can,  of  course,  change  places  occasionally.  When 
there  is  grass  under  the  trees  a  cloth  must  be  spread  to  catch  the 
beetles,  which  would  otherwise  often  be  lost.  It  will  be  very  easy 
to  clear  trees  of  smaller  size  by  shaking  them  energetically,  but 
not  violently  enough  to  break  them. 

"It  is  perhaps  in  the  canton  of  Mayenne  that  the  cockchafer 
hunt  is  pursued  by  the  inhabitants  with  the  greatest  method, 
energy,  and  perseverance.  There  those  engaged  in  the  chase  of 
the  beetles  are  divided  into  squads  of  four  (men,  women,  or 
children),  each  of  which  is  furnished  with  the  following  instru- 
ments: (i)  A  sheet  of  burlap  three  yards  by  two,  in  the  ends  of 


278  BULLETIN  NO.  44.  [May, 

which  two  flexible  sticks  are  fastened.  Strings  intended  to  sup- 
port the  apparatus  are  attached  to  these  sticks.  (2)  A  long  pole 
armed  with  an  iron  hook.  (3)  A  sack  of  coarse  cloth.  The  squad 
being  thus  equipped,  two  hold  the  sheet  extended  under  the 
branches.  Owing  to  the  flexibility  of  the  rods  at  the  end,  the 
surface  of  the  sheet  easily  takes  the  concave  form  of  a  common 
hammock.  The  branches  are  then  shaken  with  the  hand  or  with 
the  hooked  stick,  and  the  cockchafers  fall  upon  the  cloth  and 
accumulate  in  the  center." 

Between  2  and  5  o'clock  a.m.  is  the  best  time  for  capturing  our 
American  June  beetles.  If  they  are  thus  collected  in  very  great 
numbers,  they  may  be  most  conveniently  killed  by  throwing  them 
into  tubs  or  barrels  of  water  with  kerosene  on  the  surface.  If  the 
number  is  so  great  as  to  be  likely  to  be  offensive  if  left  to  decay, 
they  may  be  scattered  upon  the  fields  as  a  fertilizer. 

The  foregoing  method  is  but  little  likely  to  be  brought  into 
use  on  the  scale  required  to  make  it  effective  unless  the  white 
grubs  become,  at  least  locally,  more  destructive  than  they  are  at 
present  in  any  part  of  the  State  of  Illinois.  It  is  quite  within  the 
bounds  of  possibility,  however,  that  this  or  some  similar  method 
will  be  ultimately  forced  upon  the  American  farmer. 

Our  June  beetles  are  strongly  attracted  by  lights;  a  disposition 
which  may  be  used  for  their  destruction  in  fields.  An  apparatus 
consisting  of  a  lantern  suspended  over  a  tub  of  water,  placed  in  or 
near  trees  or  groves  resorted  to  by  the  beetles,  will  often  collect 
large  numbers  of  the  adult  insects,  which,  flying  against  the 
lantern,  drop  into  the  water,  where  they  are  readily  killed  if  a  little 
kerosene  has  been  poured  over  the  surface.  This  method  is, 
however,  of  little  value  as  compared  with  that  above  described, 
since  it  attracts  males  in  very  much  greater  proportion  than 
females — sometimes  fifty  of  the  former  to  one  of  the  latter.  It  is 
also  ineffective  on  moonlight  nights,  and  when  the  weather  is  cool 
or  windy ;  is  much  more  expensive;  and,  under  the  most  favor- 
able circumstances,  less  thoroughgoing.  Its  effect  is  shown  by 
office  notes  made  in  1888  and  1891.  June  9th  of  the  former  year 
one  hundred  and  twenty-seven  beetles  were  caught  in  a  pan  fifteen 
inches  across  partly  filled  with  water  and  kerosene,  above  which 
an  ordinary  lantern  was  suspended,  the  apparatus  being  placed  on 
a  bench  under  trees,  in  Urbana,  111.  A  similar  experiment,  made 
May  7,  1891,  with  a  tub  of  water  and  oil  and  a  common  kerosene 
lamp  yielded  1,290  beetles,  of  which  all  but  forty-one  were  males. 
In  this  case  the  trap  was  placed  in  a  small  forest  plantation  on  the 
University  farm  in  Urbana.  These  beetles  were  all  taken  between 
7:45  and  9:15  p.  m.,  after  which  only  now  and  then  one  would 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  2/9 

come  to  the  light.  Later  in  the  season  no  doubt  the  proportion 
of  females  to  males  would  have  been  greater ;  but  statements 
made  in  another  part  of  this  article,  under  the  head  "  Life  History 
and  Habits,"  show  that  the  disproportion  continues  throughout 
the  season. 

The  spraying  of  trees  most  resorted  to  for  food  is  a  possible 
measure,  since  the  beetles  are  killed  by  arsenical  poisons — a  fact 
demonstrated  by  laboratory  experiments  made  by  us  in  1888  with 
oak  leaves  dipped  in  Paris  green  mixture,  one  ounce  to  twenty 
gallons  of  water.  The  expense  of  a  general  application  of  such 
an  insecticide  will,  however,  prevent  its  common  use. 

When  pigs  can  be  turned,  in  May  and  June,  into  groves, 
orchards,  or  forests  infested  by  the  beetles,  they  cannot  fail  to 
destroy  immense  numbers  of  them,  since  they  eat  them  eagerly, 
and  can  easily  find  them,  hidden  as  they  commonly  are  by  day 
barely  under  the  surface  of  the  ground.  This  is  a  measure  only 
occasionally  applicable. 

Remedial  Measures. — Direct  remedies  for  the  attacks  of  white 
grubs  are  either  inapplicable  to  the  corn  field,  are  of  doubtful 
economic  value,  or  are  too  little  understood,  as  yet,  to  make  them 
worthy  of  recommendation.  For  example,  kerosene  emulsion 
may  properly  be  applied  to  infested  lawns,  and,  if  followed  by  a 
copious  watering,  may  kill  large  numbers  of  the  grubs,  but  the 
cost  of  this  material  and  treatment  will  preclude  its  use  against 
grubs  in  corn;  and  kainit  and  other  potash  fertilizers  (the  sulphate 
especially)  will  destroy  grubs  in  the  earth,  but  for  this  purpose 
must  be  used  at  a  rate  inadmissible  in  farm  practice — more  than  a 
ton  per  acre  according  to  Prof.  Perkins  (Fifth  Ann.  Rep.  Vt.  Agr. 
Exper.  Station,  p.  152). 

Among  remedial  measures  of  uncertain  value  may  be  men- 
tioned the  cultivation  and  dissemination  of  the  fungas  parasites  of 
the  white  grub — uncertain  because  not  yet  thoroughly  tested,  and 
because  such  tests  as  have  been  made  do  not  demonstrate  the 
practical  utility  of  the  method. 

These  parasitic  fungi  do,  however,  sometimes  spontaneously 
destroy  immense  numbers  of  white  grubs  in  the  field,  and  some  of 
them  can  be  easily  cultivated  in  quantity  outside  the  body  of  the 
insect — almost  as  easily  as  mushrooms  may  be  grown  for  the 
market.  The  subject  of  the  fungous  diseases  of  these  insects  is 
therefore  a  very  suitable  one  for  investigation,  and  should  undoubt- 
edly be  most  thoroughly  studied  from  every  point  of  view. 


280  BULLETIN   NO.   44.  [May, 

THE  GREEN  JUNE  BEETLE. 
(Allorkina  nitida,  L.) 


FIG.   48. — Green   June    Beetle:     a,  larva;   6,  pupa;   c,  male  beetle; — all    enlarged    \yz 
diameters;  d,  e,f,g,  mandible,  antenna,  leg,  and  maxilla  of  larva, — more  enlarged. 

The  larva  of  the  green  June  beetle,  Allorhina  nitida,  commonly 
known  as  a  white  grub  where  it  occurs,  is  distinguishable  from  the 
species  of  Lachnosterna  and  Cyclocephala  by  its  somewhat  larger 
size  when  full  grown;  by  the  thick  covering  of  short  stiff  hairs 
easily  visible  to  the  naked  eye;  but  especially  by' the  difference  in 
its  method  of  locomotion  upon  a  hard  surface.  The  common  white 
grubs  (Lachnosterna)  creep  only  by  means  of  their  legs,  dragging 
the  heavy  abdomen  clumsily  along;  but  the  larva  of  the  green  June 
beetle,  when  thrown  upon  a  hard  surface,  turns  immediately  upon 
its  back,  and  moves  somewhat  easily  in  this  position  by  alternate 
contraction  and  expansion  of  the  segments  of  the  body,  using  the 
stiff  hairs  upon  the  back  as  an  aid. 

This  is  a  southern  species,  and  in  the  Southern  States  largely 
replaces  Lachnosterna,  its  larva  being  there  known  as  the  white 
grub.  In  Central  Illinois  it  occurs  but  rarely,  but  becomes  notice- 
ably abundant  in  the  southern  part  of  the  State,  where  it  has  been 
occasionally  reported  as  injurious  in  a  small  way.  Although  it 
has  not  been  found  in  corn  fields,  its  food  and  habits  are  such  as  to 
make  it  altogether  likely  that  under  favoring  circumstances  it 
might  injure  corn  in  the  same  manner  as  the  Lachnosterna  larva — 
or  rather  as  the  larva  of  Cyclocephala,  which  it  more  closely 
resembles  in  its  life  history.  The  grub  is  normally  a  grass  insect, 
but  infests  likewise  strawberry  fields,  and  has  been  found  by  Dr. 
Riley  to  feed  in  confinement  upon  the  roots  of  wheat.  It  seems 
to  be  less  dependent  upon  living  vegetation  than  even  the  white 
grubs,  apparently  living  much  more  generally  upon  a  rich  soil. 
Indeed,  the  beetles  seem  to  be  attracted  to  manured  land  when 
about  to  lay  their  eggs,  or  to  that  which  has  been  heavily  mulched 
or  contains  an  unusual  amount  of  decomposing  vegetation. 
Townsend  has  found  them  living  in  clean  earth  under  circum- 
stances to  indicate  a  carnivorous  habit. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  28l 


The  life  history  of  this  insect  is,  as  already  intimated,  different 
from  that  of  Lachnosterna,  especially  in  the  fact  that  pupation  of 
the  larva  takes  place  in  May,  the  beetles  issuing  in  June.  Its 
length  of  larval  life  is  not  known,  nor  the  precise  time  or  place  of 
oviposition. 

PRIONUS   GRUBS. 


FIG.  49. — Prionus  grub  ;  natural  size. 

The  occasional  occurrence  in  corn  of  large  thick-bodied  grubs 
belonging  to  a  different  family  from  the  common  white  grubs  of 
this  article,  calls  merely  for  general  mention.  These  are  the  larvae 
of  two  species  of  large  brown,  flattish,  long-horned  beetles,  and 
belong  to  the  genus  Prionus  (P.  imbncornis  and  P.  laticollis}. 
They  are  sometimes  common  in  prairie  or  pasture  sod,  where  they 
feed  upon  the  roots  of  grass,  and  have  also  been  a  few  times 
reported  in  corn  fields  in  Illinois  and  Missouri,  doing  an  injury 
apparently  identical  with  that  of  the  white  grubs.  These  grubs 
are  at  once  distinguishable  from  the  latter  insects  by  their  greater 
size  (3  mm.  in  length  and  nearly  half  as  thick  when  full  grown), 
by  the  form  of  the  body  (tapering  from  the  head  backwards),  and 
by  the  fact  that  it  is  little,  if  at  all,  curved.  They  are,  further,  at 
once  distinguishable  by  the  rudimentary  and  inconspicuous  char- 
acter of  their  legs.  They  are  much  more  generally  known  to 
economic  entomology  for  their  injuries  to  the  roots  of  the  vine 
and  apple  and  some  forest  trees  than  for  their  agricultural  relations. 


FIG.  50. — Pupa  of  Prionus; 
natural  size. 


FIG.  51. — Beetle  of  Prionus 
laticollis;   natural  size. 


282  BULLETIN   NO.   44.  f May, 

b.     Roots  penetrated,  perforated,  irregularly  burrowed,  and  more 
or  less  eaten  off  and  eaten  up.     Underground  parts  of  stalk 
usually  also  similarly  injured. 
Wireworms  in  soil  among  the  roots. 

(For  a  discussion  of  the  wireworm  injury  to  corn,  see  this 
report,  p.  224.) 

Small,  slender,  soft-bodied,  white  or  yellowish-white  grubs  in  the 
roots  and  earth. 

THE  SOUTHERN  CORN  ROOT  WORM. 

(Diabrotica  i2-punctata,  Oliv.) 
(Fig.  52-56.) 

Injuries  to  corn  by  the  southern  corn  root  worm  have  not 
been  seen  by  us  in  Northern  Illinois  and  but  rarely  in  the  central 
part  of  the  State,  but  they  are  more  likely  to  occur  southward. 
Outside  this  State  they  have  been  recognized  by  entomologists  in 
Ohio,  Indiana,  Kentucky,  Arkansas,  Mississippi,  Louisiana,  Ala- 
bama, South  Carolina,  Virginia,  and  Maryland.  As  the  beetle 
occurs  from  Canada  southward  through  the  Atlantic  region,  and 
thence  to  Minnesota,  Kansas,  Louisiana,  and  Mexico,  it  will  prob- 
ably be  found  much  more  generally  present  in  corn  fields  than  the 
above  report  would  indicate. 

Its  injuries  are  very  similar  in  general  character  and  effect  to 
those  of  the  much  more  abundant  and  better  known  northern  corn 
root  worm  (Diabrotica  longicornis),  with  which  they  have  doubtless 
frequently  been  confounded.  They  are  distinguishable  with  some 
difficulty  from  those  due  to  the  various  species  of  wireworms,  and 
it  will  often  require  the  recognition  of  the  larva  itself  to  determine 
positively  to  which  of  these  two  classes  of  insects  a  given  root 
injury  is  due.  The  presence  of  this  root  worm  in  the  field  gives 
origin  to  the  usual  general  effects  of  the  loss  of  roots  by  the  plant, 
varying  according  to  the  age  of  the  corn,  the  gravity  of  the  injury, 
and  the  kind  of  soil  and  weather.  A  conspicuous  damage,  notice- 
able on  a  casual  inspection,  may  vary  from  the  death  of  the  plant 
to  a  slight  retardation  of  its  growth  or  to  a  general  spindling, 
yellowish,  and  unhealthy  look. 

In  the  young  plant,  about  six  inches  high,  the  characteristic 
perforations  of  the  stalk  underground  may  result  in  the  sudden 
withering  of  the  whole  plant,  or,  more  commonly,  in  the  killing  of 
the  central  leaf  or  tuft  of  growing  leaves — an  appearance  which 
has  given  to  this  insect  the  common  name  of  the  "  bud  worm  "  in 
some  of  the  Southern  States.  In  certain  instances  the  plant  has 
been  killed,  as  in  Maryland,  almost  as  soon  as  it  has  sprouted. 

As  the  season  advances,  the  corn  in  affected  fields  is  likely  to 


1896.]         INSECT   INJURIES  TO   SEED   AND   ROOT   OF   CORN.  283 

be  uneven  in  size,  and  later,  as  the  plant  becomes  top-heavy  with 
growth,  it  may  fall  to  the  earth  when  the  soil  is  softened  by  rains, 
and  especially  during  windy  storms.  Having  once  so  fallen,  it 
will,  if  badly  injured,  fail  to  rise  again;  and  it  may  further  be  seen 
that  the  plant  has  but  little  hold  upon  the  ground,  a  whole  hill, 
perhaps,  being  readily  pulled  up  with  one  hand.  As  a  consequence 
of  the  loss  of  roots  and  the  general  weakening  of  the  plant,  many 
stalks  fail  to  set  the  ear,  or  form  only  a  nubbin.  The  injured 
plant  also  matures  slowly,  remaining  green  longer  than  the  aver- 
age, and  being  thus  especially  subject  to  injury  by  frost. 

A  closer  examination  of  the  young  plant  will  commonly  show 
a  perforation  of  the  underground  part  of  the  stem  either  at  or 
near  the  upper  circle  of  roots.  Later,  as  the  corn  plant  increases 
in  size,  the  roots  themselves  are  seen  to  be  gnawed  irregularly, 
great  holes  or  notches  being  eaten  out,  first  in  one  direction  and 
then  in  another,  until  the  roots  are  severed  or  consumed.  In  the 
larger  roots  the  larva  may  perhaps  completely  bury  itself,  but  it  is 
much  more  likely  to  eat  in  and  out- irregularly  than  is  the  smaller 
northern  corn  root  worm  presently  to  be  described.  It  differs 
from  this  last  species  likewise  in  the  fact  that  it  commonly  devours 
everything  as  it  goes,  leaving  little  or  no  refuse  in  its  burrows; 
and  in  the  further  fact  that  it  works  all  along  to  some  extent  in 
the  base  of  the  stalk,  which  it  penetrates,  but  not  deeply,  finally 
causing  the  stalk  to  blacken  and  rot  where  water  gets  admission 
to  its  injuries.  Its  attack  on  corn  is  also  earlier,  briefer,  and  much 
more  vigorous  and  destructive,  owing  to  the  larger  size  of  the 
larva  and  its  more  rapid  growth  and  earlier  maturity.  Even  in 
well-grown  corn  it  very  commonly  bores  into  the  stalk  beneath 
the  upper  circle  of  brace  roots,  or  behind  the  sheath  of  the  lower 
leaf— ^habits  in  which  it  differs  from  the  northern  corn  root  worm. 

Search  for  this  root  worm  should  be  made  in  or  about  the 
injured  parts — from  the  middle  of  May  to  the  middle  of  August  in 
the  latitude  of  the  southern  half  of  Illinois.  It  is  a  soft,  slender- 
bodied,  worm-like  insect,  a  little  over  half  an  inch  in  length  when 
full  grown,  and  nearly  ten  times  as  long  as  thick.  The  surface  is 
slightly  wrinkled  or  warty,  white  when  young,  and  yellowish  when 
old.  The  head  is  dark  brown,  sometimes  nearly  black,  and  there 
is  a  pale  brown  leathery  patch  on  the  top  of  the  segment  next 
behind  the  head,  and  a  nearly  circular  similar  patch  on  the  top  ,of 
the  last  segment  of  the  body.  The  legs  are  very  short  and  small, 
and  the  skin  bears  only  a  few  long  scattered  hairs. 


284 


BULLETIN   NO.   44. 


FIG.  52. — Southern  Corn  Root  Worm,  dorsal  view;  enlarged  five  diameters. 

JL. 


FIG.  53.— The  same,  side  view. 

It  seems  most  likely  to  attack  early  planted  corn,  and  hence 
in  the  Northern  States  has  been  found  most  frequently  in  sweet 
corn.  An  injury  of  fifty  per  cent,  is  a  not  unusual  effect  of  its 
presence  in  Southern  Illinois,  and  elsewhere  it  has  been  reported 
as  sometimes  destroying  almost  every  hill  when  the  corn  was  young. 
This  corn  root  worm  has  not  been  taken  in  the  act  of  injury 
to  the  roots  of  any  other  plant  than  corn,  but  has  once  been  seen 
eating  off  a  stem  of  young  wheat  in  fall.*  Lugger  found  the  pupae 
among  the  roots  of  a  common  prairie  plant,  the  cone  flower  (Rud- 
beckia),  but  says  nothing  of  injury  to  that  plant;  and  my  assistant, 
Mr.  Marten,  reports  the  occurrence  of  young  larvae  among  the 
roots  of  Cyperus  strigosus  and  Scirpus  fluviatilis — two  sedges  com- 
mon in  moist  low  lands,  the  roots  of  which  presented  the  same 
appearance  of  injury  as  those  of  infested  corn. 

The  food  of  the  adult  Diabrotica  12- 
punctata  is  widely  varied,  apparently 
much  more  so  than  that  of  the  northern 
Diabrotica.  It  has  been  for  a  long  time 
commonly  known  as  a  squash  beetle, 
eating  both  leaves  and  green  fruit  of 
squashes,  melons,  and  cucumbers.  We 
have  seen  it  eating  into  pumpkins, 
sometimes  to  the  depth  of  half  an 
inch,  and  feeding  upon  clover  blossoms 
and  upon  the  leaves  of  tame  and  wild 
sunflowers  (Helianthus).  We  have  found 
it  in  May  eating  away  the  edges  of  the 
leaves  of  young  corn  in  the  field,  and  in 
July  and  August  making  small  round 
holes  in  corn  leaves  in  our  breeding 
cages.  In  September  and  October  it  has 
occasionally  been  taken  from  the  tip  of 


FIG.  54.  —  Beetle  of  Southern 
Corn  Root  Worm;  enlarged 
five  and  two-thirds  diameters. 


*  Webster,  in  Bull.  45  (1892),  Ohio  Agr.  Exper.  Station,  p.  203. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  285 

the  ear  of  corn,  feeding  on  the  silk,  and  once  in  August  we  saw 
it  gathering  up  fallen  corn  pollen.  It  has  also  fed  upon  ragweed 
leaves  in  our  breeding  cages  in  August.  By  other  observers  it 
has  been  reported  to  feed  on  the  petals  of  various  flowers,  includ- 
ing roses,  dahlias,  cosmos,  and  the  cotton  plant;  upon  young 
volunteer  oats  (December),  on  certain  moulds,  on  the  horse  nettle 
(Solanum  canadense),  on  cabbage,  cauliflower,  and  beans;  and  on 
the  leaves  of  plums,  cherries,  apricots,  and  raspberries.  Webster 
has  also  seen  it  eating  unripe  kernels  of  wheat  and  corn. 

LIFE   HISTORY. 

As  is  very  commonly  the  case  with  American  injurious  insects, 
the  life  history  of  this  beetle  is  incomplete.  Our  studies  of  it  are 
deficient  not  only  in  continuity  of  experimental  work,  but  even  in 
a  number  and  distribution  of  observations  and  collections,  sufficient 
to  give  us  a  fair  ground  of  probable  inference.  We  are  especially 
uncertain  as  to  the7number  of  broods  and  the  stage  or  stages  of 
hibernation.  In  the  latitudes  of  Central  and  Southern  Illinois  it 
seems  most  likely  that  this  is  a  two-brooded  insect,  but,  if  so,  data 
published  from  Alabama  and  Mississippi  would  make  it  extremely 
probable  that  it  is  three-brooded  there.  Webster's  observations 
in  Indiana  would  lead  us  to  suppose  that  it  hibernates  as  an  adult, 
he  having  found  it  feeding  upon  volunteer  oats  as  late  as  Decem- 
ber I4th,  and  abroad  in  spring  as  early  as  April  l/th,  at  which  time 
the  sexes  appeared  in  copula. 

Our  own  voluminous  collection  records  of  the  adult  do  not 
clearly  bear  out  the  suppositions  made  above  concerning  the 
hibernation  and  the  number  of  annual  generations  of  this  species. 
Without  ever  having  made  any  special  search  for  it,  I  find  that  we 
have  actually  obtained  it  in  eighty-two  collections, — mostly  of  a 
miscellaneous  character, — ranging  from  April  20th  to  November 
1 5th.  We  have  thus  taken  the  imago  once  in  April,  six  times  in 
May,  eight  times  in  June,  sixteen  times  in  July,  twenty-eight  in 
August,  eighteen  in  September,  four  in  October,  and  once  in 
November — a  gradual  rise  in  frequency  from  April  to  August,  and 
a  similar  gradual  decline  thence  to  the  end  of  the  season.  In  our 
special  collections  of  hibernating  insects  this  species  has  not, 
appeared;  and  in  our  large  electric-light  collections,  made  from 
May  to  September  in  1886  and  1887,  it  occurred  infrequently,  and 
in  no  case  until  July. 

As  we  now  understand  the  subject  we  may  say  that  in  the 
latitude  of  the  southern  half  of  the  State  the  eggs  are  laid  in  May 
and  June,  that  the  root  worms  do  the  greater  part  of  their  mischief 
also  in  these  months,  pupating  from  the  middle  of  June  to  the  last 


286 


BULLETIN   NO.   44. 


\Mayy 


of  July,  and  yielding  the  beetle  in  July  and  August.  The  new 
generation  commence  to  pair  by  the  beginning  of  the  month  last 
mentioned,  and  young  larvae  of  the  generation  following  may  be 
found  early  in  September. 

I  need  only  add  that  the  eggs  are  placed,  either  singly  or  in 
groups  of  two  to  twelve  or  more,  according  to  Riley's  observations, 
below  the  surface  of  the  soil  near  the  plants,  in  cracks  or  imme- 
diately about  the  base  of  the  plants. 


FIG.  55. — Pupa  of  Southern  Corn  Root 
Worm,  dorsal  view;  enlarged  ten 
diameters. 


FIG.  56. — Ventral  view  of  same 


NATURAL  ENEMIES. 

So  far  as  now  known,  the  most  effective  natural  check  on  the 
multiplication  of  this  insect  is  a  bacterial  parasite  {Bacillus  rufans) 
observed  by  me  to  infest  the  larva,  killing  about  three-fourths  of 
a  considerable  collection  of  these  corn  root  worms  brought  from 
Jacksonville  July  19,  1889.  We  do  not  yet  know  what  part  of 
the  larva  is  first  attacked  by  this  Bacillus,  but  by  the  time  the 
resulting  disease  has  reached  a  fatal  stage,  it  swarms  in  all  the 
fluids  of  the  root  worm,  which  have  become  practically  a  pure 
culture  of  this  bacterial  species.  Infested  larvae  lose  their  charac- 
teristic yellowish  tinge,  becoming  gray  and  somewhat  swollen,  and 
after  death  they  change  color  through  pinkish  to  dull  dark  red, 
the  internal  organs  breaking  up  to  a  fluid  pulp,  held  for  a  con- 
siderable time  in  the  tough  cuticle  of  the  dead  larva.  The  fluids 
of  such  specimens  have  a  milky  appearance  in  the  pale  worms  and 
a  reddish  tint  in  the  others.  This  last  color  is  due,  not  to  the 
color  of  the  bacilli  themselves,  but  to  an  excreted  coloring  matter 
diffused  through  the  fluids  in  which  they  grow.  In  artificial 


1896.]         INSECT   INJURIES  TO   SEED   AND   ROOT   OF   CORN.  287 

cultures,  consequently, — a  number  of  which  I  made  in  1889, — a 
similar  color  is  imparted  to  the  culture  medium,  whether  this  be 
solid  or  fluid. 

I  have  discovered  no  insect  enemy  of  this  species,  but  Dr. 
Riley  reports  the  rearing  of  two  dipterous  parasites  of  it;  one 
from  the  larva  and  pupa,  and  one  (a  tachinid)  from  the  beetle. 
Professor  H.  Garman  notes  the  occurrence  of  small  numbers  of 
predaceous  beetles  and  larvae  in  summer  and  fall  with  young  root 
worms  in  the  earth.  He  also  mentions  some  internal  parasites  of 
the  imago — Gregarinae  and  nematoid  worms. 

Notwithstanding  the  abundance  of  the  adult  Diabrotica  and 
its  general  distribution  upon  a  great  variety  of  plants,  it  seems  but 
little  noticed  by  birds.  It  has  occurred  but  once  in  my  own 
studies  of  the  food  of  birds  (in  July,  eaten  by  a  catbird),  and  was 
not  once  recognized  by  Dr.  Riley's  assistants  in  their  studies  of 
the  contents  of  the  stomachs  of  one  hundred  and  two  English 
sparrows  which  had  eaten  insects. 

REMEDIAL   MEASURES. 

Until  the  life  history  of  this  species  is  better  known,  measures 
of  prevention  or  of  remedy  can  scarcely  be  intelligently  discussed. 
The  fact  that  its  injuries  to  corn  occur  without  apparent  reference 
to  the  crop  of  the  previous  year  makes  it  unlikely  that  the  favorite 
method  of  rotation  will  serve  for  the  protection  of  corn  against 
this  species.  According  to  the  scattered  observations  hitherto 
reported  sweet  corn  seems  to  be  much  more  liable  to  injury  than 
the  field  varieties,  from  which  fact  we  may  surmise  that  the  time 
of  planting  has  something  to  do  with  the  intensity  of  the  attack. 
The  vicinity  of  cucumbers,  squashes,  and  other  of  the  commoner 
food  plants  of  the  beetle  may,  however,  account  for  this  seeming 
preference. 

c.  Roots  visibly  penetrated  and  perforated  scarcely  at  all;  some- 
times decayed  at  tips,  but  not  eaten  away.  Principal  injury 
interior,  in  form  of  minute  burrows  which  are  commonly 
longitudinal. 

THE  NORTHERN  CORN  ROOT  WORM. 
(Diabrotica  longicornis,  Say.) 

(Fie.  57-6i.) 

The  northern  or  common  corn  root  worm  (Diabrotica  longi- 
cornis}  is  by  far  the  most  destructive  corn  root  insect  dependent 
on  that  plant  alone.  Indeed,  it  now  seems  likely  that  if  it  were 
not  for  the  fact  that  it  is  highly  susceptible  to  a  measure  of  pre- 
vention which  farmers  have  very  generally  taken  unconsciously, 


288  BULLETIN  NO.  44.  [May, 

as  a  part  of  a  sound  agricultural  routine,  it  would  long  ago  have 
seriously  threatened  the  profitable  continuance  of  corn  culture  in 
the  very  part  of  the  country  best  adapted  to  that  great  crop. 
Even  as  it  is,  its  injuries  are  undoubtedly  to  be  reckoned  by 
millions  of  dollars  annually*,  although  the  essential  facts  concern- 
ing its  ravages  and  their  ready  and  complete  prevention  were 
officially  and  widely  published  nine  years  ago.t 


FIG.  57. — Northern  Corn  Root  Worm;  enlarged  six  diameters. 

INJURIES   TO   CORN. 

The  presence  of  this  insect  first  betrays  itself  in  badly  infested 
fields  when  the  plant  is  a  foot  or  so  high.  If  at  this  time  patches 
of  corn  are  observed  which  seem  to  be  standing  still,  so  that 
the  plants  adjacent  leave  them  behind,  giving  the  field  an  uneven 
appearance,  it  is  'possible — especially  if  the  field  has  been  in  corn 
two  years  or  more  preceding — that  this  retardation  of  growth 
is  due  to  the  presence  of  this  corn  root  worm.  In  this  case,  if 
the  corn  be  pulled  up,  many  of  the  larger  roots  will  be  seen  to 
be  short  and  stubbed  and  rotten  at  the  ends.  On  others  a  dead- 
ened brown  line  will  be  found,  running  irregularly  lengthwise, 
while  still  other  roots  may  be  dead  their  whole  length.  Possibly 
when  the  earth  is  shaken  off  a  slender  white  grub  will  be  discov- 
ered, two-fifths  of  an  inch  long  and  about  as  thick  as  a  pin ;  but 
more  frequently  the  observer  must  carefully  split  or  peel  some  of 
the  affected  roots,  when  a  slender  sinuous  brown  burrow  filled 
with  excrement  will  be  exposed,  running  from  one  end  of  the  root 
to  the  other,  usually  with  the  root  worm  just  mentioned  some- 
where in  its  course.  This  grub  is  white,  except  the  head,  the  top 
of  the  first  segment  of  the  body,  and  a  little  patch  on  the  last  seg- 
ment, which  are  yellowish  brown.  The  body  is  smooth  and 
cylindrical,  the  head  is  short,  deep,  and  rounded,  and  the  tip  of 
the  body  is  also  bluntly  rounded  off,  somewhat  like  that  of  a  com- 
mon grub.  These  last  characters  will  serve  to  distinguish  it  from 
small  wireworms  which  are  often  found  in  such  situations,  but 
which  are  usually  flattened  from  above,  especially  at  the  head, 
while  in  them  the  end  of  the  body  is  commonly  more  or  less 
toothed  or  notched  or  pointed.  The  grubs  or  larvae  of  several 

*  Webster  estimates  the  damage  to  corn  in  twenty -four  counties  of  Indiana  in  1885 
at  $2,000.000,  basing  this  judgment  on  a  loss  of  $16,000  by  one  large  farmer,  and  on  his 
personal  knowledge  of  its  distribution  and  abundance  in  that  State. 

fTwelfth  Rep.  State  Ent.  111.,  pp.  29,  30. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  289 

small  flies  will  often  be  found  about  the  roots  of  corn,  and  careless 
or  unskilled  observers  have  occasionally  mistaken  these  for  the 
corn  root  worm,  but  this  latter  insect  has  six  short  legs  on  the 
three  segments  just  behind  the  head,  while  the  grubs  of  flies  are 
footless.  We  have  seen  as  many  as  fifteen  or  twenty  to  a  hill,  and 
I  do  not  doubt  that  in  fields  heavily  attacked  they  are  much  more 
numerous.  As  the  root  dies,  however,  it  is  forsaken  and  another 
is  attacked,  until,  not  infrequently,  almost  every  root  will  become 
infested  as  fast  as  it  puts  forth.  This  damage  may  thus  extend 
to  the  practical  destruction  of  the  entire  root  growth,  and  the  con- 
sequent death  of  the  plant ;  or  it  may  remain  miserably  dwarfed — 
six  inches,  perhaps,  when  other  plants  measure  four  or  five  feet. 
If  the  stem  is  perforated  above  the  roots,  the  injury  is  probably 
due  to  the  southern  root  worm  or  to  some  of  the  species  of  wire- 
worms,  which  one  can  only  be  told  by  finding  the  insect  itself. 


FIG.  58. — Com  root  broken  across  to  show  Northern 

Corn  Root  Worm  within.  Fl£-   59-— Pupa    of    Northern 

Lorn  Root  Worm;  enlarged. 
8^  diameters. 

Attention  may  perhaps  be  first  attracted  when  the  corn  is 
putting  forth  the  silk,  by  the  extraordinary  number  of  barren 
stalks  upon  which  no  ear  is  forming,  or  stalks  may  be  seen  which 
have  scarcely  life  enough  to  tassel.  It  may  also  be  observed  that 
the  corn  is  unaccountably  late,  looking  evidently  greener  and 
younger  than  other  fields  which  had  no  advantage  at  the  start.  Or 
injury  may  be  first  suspected  during  a  period  of  drouth,  patches  here 
and  there,  or  the  entire  field,  suffering  unduly  from  this  cause.. 
The  most  conspicuous  evidence  of  this  injury,  however,  at  this 
stage  of  growth,  is  the  prostration  of  the  corn  after  a  soaking  rain 
with  wind,  and  the  evident  inability  of  the  plant  to  right  itself. 
If  one  of  the  worst  affected  stalks  be  pulled  up,  the  observer  will 
notice  that  the  roots  are  few  in  number,  that  many  of  them  are 
withered  and  brown,  and  that  others  are  rotted  away  to  stubs.  In 
these  discolored  roots  the  minute  brown  burrow  of  the  insect  may 
usually  be  detected,  and  the  corn  root  worm  itself  may  often  be 
exposed.  A  minor  attack  frequently  has  the  effect  so  to  retard 


2QO  BULLETIN   NO.   44.  [May, 

the  ripening  of  the  corn  that  it  is  not  ready  for  the  earliest  frosts, 
and  the  ear  consequently  remains  soft  and  unfit  for  use ;  or  the 
loss  of  roots  may  have  diminished  the  size  of  the  stalk  and  ear, 
leaving  a  small  nubbin  where  a  full  ear  might  have  been  expected. 

The  injury  continues  from  about  the  first  or  the  middle  of  June 
to  the  last  of  August.  As  some  of  the  larvae  mature  and  cease 
their  work  in  the  latter  half  of  June,  and  others  not  for  two 
months  later,  plants  once  infested  may  be  freed  of  the  attack,  at 
least  in  part,  by  the  pupation  of  the  root  worms,  and  others, 
spared  at  the  beginning  of  the  season,  may  become  infested  later. 
It  has  sometimes  been  observed  that  large,  rank  stalks  which  did 
not  ear  out  had  evidently  been  injured  after  the  corn  had  begun 
to  tassel ;  while  others,  which  leaned  over  at  the  root  and  then 
grew  erect,  had  been  infested  earlier  in  the  season,  but  had  thrown 
out  new  roots  after  the  root  worms  had  matured. 

It  is  a  matter  of  common  observation  that  injuries  by  this 
insect  are  most  noticeable  during  dry  years  and  upon  the  higher 
parts  of  the  field.  We  have  no  evidence,  however,  that  the  corn 
root  worms  themselves  are  more  numerous  at  such  times  or  in 
such  situations,  and  the  greater  injury  may  be  due  simply  to  the 
diminished  ability  of  the  plant  to  withstand  attack.  I  have,  in  fact, 
seen  vigorous  and  flourishing  hills  of  corn  badly  infested  during 
wet  seasons  with  no  visible  effect  upon  their  growth,  even  the 
larger,  burrowed  roots  remaining  fresh  and  efficient,  notwith- 
standing the  injury. 

In  case  no  retardation  of  growth  or  damage  to  the  crop  has 
been  observed,  less  conspicuous  mischief  may  often  be  indicated 
by  the  great  abundance  in  the  field,  late  in  July  and  in  August,  of 
a  small  grass-green  beetle  about  a  fifth  of  an  inch  in  length, 
resembling  in  shape  and  general  aspect  the  common  small  striped 
squash  beetle,  to  which,  indeed,  it  is  closely  allied.  These  beetles 
are  most  likely  to  be  seen  clustered  at  the  tip  of  the  ear  and  feed- 
ing upon  the  young  silk,  or  lurking  at  the  base  of  the  leaf  where  it 
joins  the  stalk,  feeding  there  upon  the  fallen  pollen  of  the  plant. 
They  should  also  be  looked  for  upon  the  blossoms  of  ragweed, 
smartweed,  and  other  plants  in  bloom  among  the  corn.  This  is 
the  adult  insect  to  which  the  corn  root  worm,  so-called,  has  given 
origin,  and  its  presence  in  extraordinary  numbers  in  any  field  of 
corn  is  presumptive  evidence  that  the  plant  has  suffered  earlier 
considerable  root  injury  of  the  character  above  described. 

It  is  very  rarely  that  these  phenomena  are  to  be  observed  on 
ground  not  previously  in  corn,  although  sorghum  and  broom  corn 
have  been  found  somewhat  favorable  to  the  development  of  this 
insect.  It  is  only  where  through  neglect  it  has  become  enormously 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  2QI 

abundant  in  a  f  ild  that  we  may  anticipate  its  escape  from  the  corn 
in  very  large  numbers  before  it  has  laid  its  eggs,  in  which  event, 
corn  not  succeeding  corn  may  possibly  suffer  the  following  year.* 
The  general  damage  to  a  field  is  in  the  worst  cases  sufficient  to 
destroy  the  crop  so  far  that  the  disgusted  farmer  turns  his  pigs 
into  his  corn  to  get  what  they  can,  and  makes  no  attempt  to 
harvest  his  crop.  A  badly  infested  field  was  described  to  me  by 
Dr.  Boardman  in  1882,  which  is  worthy  of  mention  as  illustrating 
one  of  the  common  effects  of  root  injury  by  this  beetle.  "I  should 
say,"  he  writes,  "  that  one-fourth  of  the  corn  in  this  field  was 
rotting  or  beginning  to  rot.  I  found,  on  cutting  an  ear  open,  that 
I  could  slice  the  cob  as  easily  as  if  it  were  a  turnip.  The  infested 
corn  [in  Stark  county]  is  yielding  from  ten  to  fifteen  bushels  per 
acre." 

Although  the  corn  root  worm  beetle  is  distributed  throughout 
the  Mississippi  Valley,  and  south  even  to  Central  America,  it 
clearly  becomes  comparatively  rare  southward,  and  has  never 
been  taken  by  us  in  Southern  Illinois  in  any  numbers,  nor  found 
injurious  in  the  larval  stage  except  in  the  northern  two-thirds  of 
the  State. 

This  root  worm  has  not  heretofore  been  certainly  found 
infesting  any  other  plant  than  corn,  and  the  amount  of  skilled 
attention  which  has  been  given  to  this  point  by  entomologists  and 
other  accurate  observers,  makes  it  practically  sure  that  it  is  so 
closely  limited  to  corn  at  the  present  time  in  Illinois  that  we  may 
base  our  economic  methods  upon  the  supposition  that  it  infests  no 
other  plant. 

FOOD   OF  THE   BEETLE. 

The  beetles,  beginning  to  appear  in  June  and  continuing  until 
November,  feed  entirely  during  this  whole  period  upon  the  softer 
and  more  delicate  parts  of  the  vegetation  present  at  the  time. 
They  collect  the  pollen  from  the  tassels  of  the  corn,  or  gather  that 
which  has  sifted  down  among  the  leaves  and  collected  at  their 
bases,  where  these  join  the  stalk.  They  also  gnaw  away  the  fresh 
silk  from  the  tip  of  the  ear  (where  they  may  often  be  found  con- 
gregated in  numbers  of  a  dozen  to  twenty,  or  more),  probably 
thus  doing  a  considerable  amount  of  mischief  by  destroying  the 
silk  before  it  has  served  for  the  fertilization  of  the  grain,  and 
causing  thus  a  partial  blasting  of  the  ear.  They  often  eat  the 
pollen  of  smartweed  and  ragweed  among  the  corn,  and  outside  the 

*  As  an  example  of  this  tendency  to  spread  from  the  infested  field,  I  may  note  the 
not  uncommon  occurrence  at  Rankin,  111.,  July  i,  iSSy,  of  this  corn  root  worm  in  a  field 
of  corn  following  oats,  but  only  on  that  part  of  it  which  bordered  an  infested  field  in 
corn  the  previous  year.  It  is  possible  that  other  instances  of  this  kind  reported  previous 
to  1891  may  have  related  to  the  southern  corn  root  worm,  Diabrotica  i2-pimctata. 


BULLETIN   NO.   44. 


[May, 


fields  are  very  abundant  upon  thistle  blossoms,  and  likewise  upon 
heads  of  red  clover,  the  pollen  and  petals  of  which  they  feed  upon. 
By  Professor  French,  of  Carbondale,  111.,  they  are  said  sometimes 
to  infest  the  bean  plant ;  Dr.  Boardman,  of  Stark  county,  reported 
them-  as  abundant  on  cucumber  and  squash  vines ;  and  we  have 
repeatedly  seen  them  late  in  the  year  (October  nth  to  December 
i6th)  gnawing  into  ripe  pumpkins  in  the  field,  eating  through  the 
outer  hard  coat,  and  burying  themselves  in  the  pulp  to  a  depth  of 
nearly  half  an  inch.  We  have  found  them  feeding  on  flowers  of 
Helianthus,  goldenrod,  and  other  Compositae,  and  on  the  pollen  of 
sorghum  and  of  squash  ;  and  Professor  Webster  has  seen  them  on 
the  blossoms  of  the  cotton  plant.  A  farmer  in  DeKalb  county 
asserts  that  they  eat  the  pulp  of  apples  where  the  skin  has  been 
broken  from  some  other  cause,  enlarging  such  injuries  so  as  seri- 
ously to  damage  the  fruit.  This  same  fact  was  reported  to  me 
some  years  ago  from  Grundy  county,  by  Mr.  O.  B.  Galusha,  then 
Secretary  of  the  State  Horticultural  Society,  thin-skinned  apples 
apparently  suffering  worst  and,  according  to  the  judgment  of  my 
informant,  being  thus  injured  without  the  assistance  of  other 
insects.  They  have  been  repeatedly  detected  by  us  beneath  the 
husks  of  ears  of  corn,  where  the  tips  had  been  exposed  or  injured 
by  birds  or  grasshoppers,  feeding  here  on  the  broken  grains.  In 
one  instance  the  beetle  had  apparently  made  its  way  through  the 
husk  itself,  and  was  feeding  upon  the  soft  grains  beneath.  By 
Professor  Burrill,  of  the  University  of  Illinois,  it  was  found  in  1889 
(September  30th)  feeding  upon  a  fungus  belonging  to  the  genus 


Fig.  60. — Beetle  of  Northern  Corn  Root 
Worm  ;  enlarged  ten  diameters. 


FIG.  61. — Egg  of  this  species; 
enlarged  eighty  diameters. 


1896.]         INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  293 

Phallus ;  and  I  demonstrated  by  dissections  in  1882  the  fact  that  it 
sometimes  feeds  largely  on  the  smaller  fungi — blights,  rusts,  etc.* 

LIFE   HISTORY. 

This  species  is  single-brooded,  as  far  as  known.  Although  a 
few  beetles  may  occasionally  linger  late  in  open  winters, — to 
December  i6th  of  the  present  year  (1892)  for  example, — and  as  a 
rare  exception  may  even  pass  the  winter  alive,  the  species  hiber- 
nates almost  invariably  as  an  egg  in  the  earth. t  As  a  rule,  which 
is,  so  far  as  known,  practically  without  exception,  these  eggs  are 
deposited  in  fields  of  corn  and  hatch  there  the  following  spring — 
at  just  what  date  has  not  been  precisely  ascertained.  The  larvae 
have  first  been  detected  in  Central  Illinois  June  loth.  They  were 
found  by  me  less  than  half  grown  near  Polo,  in  Northern  Illinois, 
June  14,  1883.  As  the  beetle  was  reported  by  an  excellent  ob- 
server (Dr.  E.  R.  Boardman)  to  have  occurred  one  season  in 
southeastern  Iowa  as  early  as  June  25th,  some  larvae  must  hatch 
by  the  beginning  of  that  month.  Pupation  can  scarcely  begin 
later  than  June  2Oth  if  Dr.  Boardman's  date  for  the  beetle  is  correct, 
and  the  same  observer  reports  the  finding  of  the  pupa  itself  in  the 
earth  June  29th.  On  the  other  hand,  larvae  ready  for  pupation 
have  occurred  in  our  collections  as  late  as  August  26th — giving  a 
period  of  something  over  two  months  for  the  pupation  of  an 
entire  generation. 

The  extreme  dates  definitely  fixed  for  the  next  transforma- 
tion— the  emergence  of  the  beetle — are  June  25th  for  the  earliest 
and  not  earlier  than  August  3ist  for  the  last — again  a  period  of 
something  more  than  two  months.  We  have  seen  the  beetles 
copulating  at  various  dates  from  July  I9th  to  September  25th, — an 
interval  of  two  months  and  six  days, — observations  which  probably 
fix  approximately  the  beginning  and  the  end  of  oviposition.  The 
eggs,  however,  were  not  all  laid  by  October  I,  1882,  as  I  deter- 
mined by  dissecting  females  at  the  time.  For  the  present  we  may 
assign  August  1st  and  October  5th  as  the  average  dates  for  the 
first  and  last  deposit  of  eggs. 

The  recognition  of  this  eight  or  nine  weeks'  period  for  the 
passage  of  the  whole  of  a  brood  from  one  stage  to  another,  enables 
us  to  say  with  some  assurance  that  the  eggs  laid  during  this  long 
interval  in  one  year  will  hatch  through  a  corresponding  interval 

"Twelfth  Rep.  State  Ent.  111.,  p.  23. 

fl  have  in  my  office  collection  two  specimens  (one  male  and  one  female)  obtained 
March  14,  1883,  at  Normal,  111.,  with  a  quantity  of  miscellaneous  insects  collected  from 
their  hibernating  quarters.  On  the  other  hand,  beetles  collected  from  pumpkins  at 
Urbana,  November  2,  1892,  and  placed  in  breeding  cages  with  pieces  of  pumpkin  as 
food,  had  died  in  large  numbers  by  November  2oth ;  a  very  few  were  still  alive  Decem- 
ber 4th ;  two  remained  December  i7th  ;  but  December  28th  all  were  dead. 


294  BULLETIN  NO.  44.  \May, 

the  year  following — approximately  from  May  igth  to  July  1 5th, 
or  a  little  later.  While  these  dates  are,  some  of  them,  inferred,, 
there  is  no  doubt  of  the  extension  of  each  stage  of  the  develop- 
ment over  as  long  a  period  as  that  here  given ;  namely,  two 
months  to  nine  weeks.  We  have  no  precise  observations  concern- 
ing the  length  of  life  of  any  individual  in  any  one  stage ;  neither 
do  we  know  the  number  of  eggs  laid  by  each  female,  except  as 
an  inference  from  dissections.  I  have  counted  as  many  as  fifty 
well-formed  eggs  of  nearly  full  size  in  the  ovaries  of  a  single 
female  beetle. 

HABITS   OF   BEETLE  AND   LARVA. 

The  growing  larvae  remain  concealed  from  view  within  the 
roots,  burrowing,  not  through  the  middle  but  nearer  the  surface, 
in  a  slightly  sinuous  longitudinal  direction,  sometimes  from  the 
stalk  outwards,  but  more  frequently  mining  inwards  from  the  outer 
end  of  the  root.  They  have  considerable  power  of  locomotion 
when  removed  from  their  burrows,  and  seem  capable  of  going 
from  one  root  to  another.  Indeed,  the  fact  that  they  must  con- 
centrate in  hills  of  corn  after  hatching,  demonstrates  their  power 
of  locomotion  when  still  very  young.  It  is  altogether  likely,  con- 
sequently, that  if  a  hill  of  corn  is  killed  by  them  before  they  have 
reached  maturity,  they  will  be  entirely  able  to  search  out  another. 

When  full  grown  they  leave  the  root  preliminary  to  pupation, 
shortening  up  and  changing  to  the  pupa  stage  in  the  dirt  close  by. 
At  this  time  they  may  often  be  found  in  considerable  numbers  by 
pulling  up  infested  corn  and  shaking  out  the  dirt  from  the  roots. 
The  beetles  emerge  from  the  pupa  under  ground,  and,  coming  to 
the  surface,  most  commonly  crawl  up  the  stalk  of  corn  adjacent. 
When  recently  transformed  they  are  of  a  pale  yellowish  color,  with 
scarcely  a  tinge  of  green.  Their  first  food  consists,  as  already 
mentioned,  of  the  softer  tissues  of  the  corn  plant  itself,  especially 
of  the  silk  at  the  tip  of  the  ear,  or  the  pollen  from  the  tassel,  or 
sometimes  of  the  soft  kernels,  especially  if  these  have  been 
exposed  by  any  injury  to  the  husks.  They  also  spread  to 
various  blossoming  weeds  in  the  field,  and  after  a  time  begin  to 
desert  the  corn  field,  scattering  elsewhere  for  food.  It  is  com- 
monly towards  the  last  of  August  that  they  are  first  noticeably 
frequent  on  thistle  blossoms,  heads  of  clover,  and  other  outside 
blooming  plants.  They  do  not,  however,  leave  the  corn  fields 
generally  for  some  time  thereafter,  but  may  be  found  there  in 
greatly  diminished  numbers  at  least  as  late  as  the  middle  of 
October. 


1896.]          INSECT   INJURIES   TO   SEED   AND   ROOT   OF   CORN.  295 

How  soon  after  pairing  their  eggs  are  laid  we  do  not  now 
know;  neither  has  the  process  of  oviposition  ever  been  directly 
witnessed.  The  frequent  occurrence  of  dead  female  beetles  (in 
October  and  November)  in  the  earth  in  corn  fields  in  the  midst  of 
the  eggs,  and  the  distribution  of  the  eggs  themselves,  is,  however, 
sufficient  evidence  that  the  beetle  enters  the  earth  to  lay  her  eggs, 
and  that  she  may  perish  there  after  her  ovaries  are  spent.  .Al- 
though the  eggs  of  this  beetle  have  never  been  found  outside  of 
corn  fields,  notwithstanding  extensive  search  in  many  other  situa- 
tions, it  is  certain  that  the  eggs  are  not  necessarily  all  laid  before 
the  female  leaves  the  field  in  which  she  emerged.  I  have,  on  the 
contrary,  frequently  proven  by  dissection  of  beetles  taken  from 
flowers  by  roadsides,  in  meadows,  and  the  like,  that  females  thus 
dispersed  may  still  contain  eggs  in  large  numbers.  A  considerable 
part  of  the  beetles,  and  apparently  the  greater  part,  do,  however, 
lay  their  eggs  under  ordinary  circumstances  before  they  leave  the 
field  of  corn;  and  it  is  also  highly  probable  on  general  grounds 
that  those  which  go  elsewhere  in  search  of  food  return  to  corn 
fields  for  oviposition.  Since  the  larva  is  not  known  to  infest  any 
other  plant  than  corn,  or,  indeed,  to  be  capable  of  living  upon  any 
other,  it  is  altogether  likely  that  the  female  instinctively  searches 
out  the  corn  plant  when  seeking  a  place  of  deposit  for  her  eggs. 

As  this  is  a  surmise  or  inference,  however,  and  not  a  matter  of 
observation,  it  remains  possible  that  if  the  corn  root  worm  is  neg- 
lected it  may  in  time  accumulate  in  such  numbers  as  no  longer  to 
confine  its  chief  injuries  to  fields  previously  in  corn,  but  that  the 
beetles,  forced  to  scatter  early,  in  search  of  food,  from  the  fields  in 
which  they  emerge  will  deposit  their  eggs  freely  everywhere  in  the 
ground,  instead  of  being  confined  as  now  chiefly  to  corn  fields.  It 
is  probably  in  fields  of  clover  that  this  is  most  likely  to  occur, 
since  the  beetles  sometimes  become  abundant  there,  feeding  upon 
the  pollen  of  the  second  growth. 

The  depth  at  which  the  eggs  are  laid  varies  from  an  inch  to 
five  or  six  inches,  the  greater  part  of  them  being  near  the  surface 
of  the  ground.  They  are  usually  deposited  in  bunches  of  three  or 
four  to  eight  or  ten,  within  a  space  of  half  an  inch  across,  not  in 
contact  with  each  other,  nor  in  any  cell  or  cavity,  but  always 
simply  scattered  in  the  earth.  Most  careful  examinations  made  in 
1882,  and  many  times  repeated,  of  the  earth  between  the  rows,  and 
of  the  roots  of  all  the  weeds  growing  in  the  field,  have  failed  to 
discover  so  much  as  a  single  egg  outside  a  space  a  few  inches 
across,  around  each  hill.  A  similar  careful  search  of  the  roots  of 
thistles,  ragweeds,  and  goldenrod  outside  the  fields,  upon  the 
flowers  of  which  the  beetles  were  feeding  in  great  numbers,  had  a 


296  BULLETIN    NO.   44.  [May, 

similar  result;  and  we  have  found  no  evidence  in  the  roots  of 
these  plants,  either  in  the  corn  fields  or  elsewhere,  that  they  have 
ever  been  infested  by  the  larvae.  In  short,  not  the  slightest  direct 
proof  has  thus  far  been  found  that  the  beetle  breeds  anywhere 
except  in  fields  of  corn.  It. is  very  probable  that  a  few  develop  in 
other  situations;  but  the  number  seems  to  be  so  small  as  to  defy 
discovery,  except  by  accident. 

PREVENTION   AND   REMEDY. 

A  judicious  rotation  of  crops  is  so  simple  and  complete  a  pre- 
ventive measure,  that  remedies  for  injury  to  corn  by  the  northern 
corn  root  worm  are  practically  unnecessary.  The  eggs  being  laid 
in  corn  ground  in  the  fall  and  the  larvae  hatching  the  following 
spring,  feeding  so  far  as  known  upon  nothing  else  but  corn,  the 
planting  of  such  infested  land  to  any  other  grain  must  inevitably 
lead  to  the  starvation  of  the  young  when  they  hatch  in  spring. 
This  is  not  an  inference  from  the  life  history  of  the  insect  merely, 
but  even  before  the  time  and  place  of  oviposition  were  known,  it 
had  been  commonly  noticed  that  corn  was  rarely  if  ever  liable  to 
injury  by  this  insect  if  planted  on  ground  which  had  borne  any 
other  kind  of  crop  the  preceding  year.  I  have,  however,  some 
reason  to  suppose  that  sorghum  and  broom  corn  are  not  good 
crops  to  follow  with  corn  when  this  root  worm  is  present. 

The  frequency  of  the  rotation  must  depend  upon  oircum- 
stances,  and  especially  upon  the  general  abundance  of  the  insect 
at  the  time.  I  know  of  no  part  of  Illinois  in  which  corn  is  not  safe 
for  at  least  two  years,  and  in  many  situations  another  year  may 
be  added  to  this  period.  No  field  on  which  the  crop  has  already 
suffered  to  any  noticeable  extent  should  be  planted  to  corn  the 
following  year  ;  and  it  will  likewise  be  prudent  to  avoid  continuing 
in  corn  any  field  in  which  the  grass-green  beetle  of  this  species  is 
seen  to  be  abundant  in  September  and  October. 

The  only  other  preventive  measure  worthy  of  mention  is  one 
equally  to  be  commended  as  a  general  agricultural  practice ; 
namely,  the  maintenance  of  the  fertility  of  the  soil  by  the  use  of 
manures,  etc.  This  will  not,  so  far  as  known,  diminish  in  any  way 
the  amount  of  insect  attack,  but  it  will  enable  the  plant  to  stand  a 
minor  injury  with  relatively  little  loss.  It  is  possible  that  experi- 
ments with  various  kinds  of  fertilizers  will  show  that  some  of  them, 
the  potash  salts  for  instance,  may  have  an  immediate  deleterious 
effect  upon  the-larvae  in  the  earth,  but  we  have  at  present  only  a 
speculative  basis  for  this  supposition. 

S.  A.  FORBES,  PH.  D., 

Consulting  Entomologist. 


£r<Se  ^,~.4£  t  &     \C. 


UNIVERSITY  OP  ILLINOIS-URBANE 


